# MCP Server Tool Evaluation Support
## Overview
Add support for evaluating tools from remote MCP servers without
requiring Python callables. Enables direct evaluation of any
MCP-compatible tool server.
## What's New
### Core Features
- **`MCPToolRegistry`**: Evaluate tools from a single MCP server
- **`CompositeMCPRegistry`**: Evaluate tools from multiple MCP servers
simultaneously
- **Automatic loaders**: `load_from_stdio()` and `load_from_http()` to
fetch tools from running servers
- **Automatic namespacing**: Tools prefixed with server name (e.g.,
`server_tool_name`)
- **Smart name resolution**: Use short names if unique, full names if
ambiguous
- **OpenAI strict mode**: Automatic schema conversion prevents parameter
hallucinations
### Usage
**Automatic Loading:**
```python
from arcade_evals import load_from_stdio, MCPToolRegistry
# Load tools automatically from MCP server
tools = load_from_stdio(["npx", "-y", "@modelcontextprotocol/server-github"])
registry = MCPToolRegistry(tools)
```
**Single MCP Server:**
```python
from arcade_evals import MCPToolRegistry, ExpectedToolCall
registry = MCPToolRegistry(mcp_tools)
suite = EvalSuite(catalog=registry)
suite.add_case(
expected_tool_calls=[
ExpectedToolCall(tool_name="tool_name", args={...})
]
)
```
**Multiple MCP Servers:**
```python
from arcade_evals import CompositeMCPRegistry, load_from_stdio
# Load from multiple servers
github_tools = load_from_stdio(["npx", "-y", "@modelcontextprotocol/server-github"])
slack_tools = load_from_stdio(["npx", "-y", "@modelcontextprotocol/server-slack"])
composite = CompositeMCPRegistry(
tool_lists={
"github": github_tools,
"slack": slack_tools,
}
)
suite = EvalSuite(catalog=composite)
suite.add_case(
expected_tool_calls=[
ExpectedToolCall(tool_name="github_list_issues", args={...})
]
)
```
## Implementation
### Files Changed
- **`libs/arcade-evals/arcade_evals/registry.py`** (NEW): Registry
abstractions and implementations
- **`libs/arcade-evals/arcade_evals/loaders.py`** (NEW): Automatic tool
loading from MCP servers
- **`libs/arcade-evals/arcade_evals/eval.py`** (MODIFIED): Enhanced
`ExpectedToolCall` and evaluation logic
- **`libs/arcade-evals/arcade_evals/__init__.py`** (MODIFIED): Exported
new registries and loaders
### Key Technical Details
- Added `BaseToolRegistry` interface for abstraction
- `MCPToolRegistry` handles single server tools
- `CompositeMCPRegistry` manages multiple servers with collision
detection
- `load_from_stdio()` and `load_from_http()` for automatic tool
discovery
- Fixed name normalization bug: MCP tools use underscores (not dots)
- Optimized tool copying: 2.5x faster via shallow copy
## Testing
- ✅ 41 tests passing (25 new tests added)
- ✅ `test_eval_mcp_registry.py`: MCPToolRegistry functionality
- ✅ `test_eval_composite_mcp.py`: CompositeMCPRegistry with multiple
servers
- ✅ Verified backward compatibility with Python tools
## Backward Compatibility
✅ **100% backward compatible** - No breaking changes
## Breaking Changes
**None**
<!-- CURSOR_SUMMARY -->
---
> [!NOTE]
> Adds end-to-end eval UX: examples, a robust CLI runner, and rich
outputs.
>
> - **New examples**: `eval_arcade_gateway.py`,
`eval_stdio_mcp_server.py`, `eval_http_mcp_server.py`,
`eval_comprehensive_comparison.py` with timeouts, error handling, and
track-based comparisons; detailed `README.md`
> - **CLI runner**: `arcade_cli/evals_runner.py` to execute
evals/capture in parallel with progress, error isolation, failed-only
filtering, context inclusion, and multi-provider/model support
> - **Output formatters**: `arcade_cli/formatters/` (txt, md, html,
json) for evals and capture; comparative and multi-model HTML with tabs
and context rendering
> - **Display refactor**: `display.py` now supports writing multiple
formats, failed-only disclaimers, include-context, and improved console
summaries
>
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
ff8acf9c34a6b61462a019a1ee9df081006517d0. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->
---------
Co-authored-by: Francisco Liberal <francisco@arcade.dev>
Co-authored-by: Mateo Torres <torresmateo@gmail.com>
180 lines
7 KiB
Python
180 lines
7 KiB
Python
"""Capture mode mixin for EvalSuite.
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This module provides the capture functionality as a mixin class,
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keeping it separate from the main evaluation logic in eval.py.
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"""
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from __future__ import annotations
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import asyncio
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from typing import TYPE_CHECKING, Any
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from arcade_evals.capture import CapturedCase, CapturedToolCall, CaptureResult
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if TYPE_CHECKING:
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from arcade_evals._evalsuite._comparative import ComparativeCaseBuilder
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from arcade_evals._evalsuite._providers import ProviderName
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from arcade_evals._evalsuite._tool_registry import EvalSuiteToolRegistry
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from arcade_evals._evalsuite._tracks import TrackManager
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from arcade_evals._evalsuite._types import EvalRubric
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from arcade_evals.eval import EvalCase
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class _EvalSuiteCaptureMixin:
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"""Mixin providing capture mode functionality for EvalSuite."""
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# These attributes are defined in EvalSuite
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name: str
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cases: list[EvalCase]
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max_concurrent: int
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rubric: EvalRubric
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_internal_registry: EvalSuiteToolRegistry | None
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_comparative_case_builders: list[ComparativeCaseBuilder]
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_track_manager: TrackManager
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# These methods are defined in EvalSuite
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async def _run_openai(
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self,
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client: Any,
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model: str,
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case: EvalCase,
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registry: EvalSuiteToolRegistry | None = None,
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) -> list[tuple[str, dict[str, Any]]]:
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raise NotImplementedError # Implemented in EvalSuite
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async def _run_anthropic(
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self,
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client: Any,
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model: str,
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case: EvalCase,
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registry: EvalSuiteToolRegistry | None = None,
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) -> list[tuple[str, dict[str, Any]]]:
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raise NotImplementedError # Implemented in EvalSuite
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def _process_tool_calls(
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self,
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tool_calls: list[tuple[str, dict[str, Any]]],
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registry: EvalSuiteToolRegistry | None = None,
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) -> list[tuple[str, dict[str, Any]]]:
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raise NotImplementedError # Implemented in EvalSuite
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def _create_eval_case(self, *args: Any, **kwargs: Any) -> EvalCase:
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raise NotImplementedError # Implemented in EvalSuite
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async def capture(
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self,
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client: Any, # AsyncOpenAI | AsyncAnthropic
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model: str,
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provider: ProviderName = "openai",
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include_context: bool = False,
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) -> CaptureResult:
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"""
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Run the evaluation suite in capture mode - records tool calls without scoring.
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Capture mode runs each case and records the tool calls made by the model,
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without evaluating or scoring them. This is useful for:
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- Generating expected tool calls for new test cases
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- Debugging model behavior
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- Creating baseline recordings
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Handles both regular cases and comparative cases. For comparative cases,
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each track is captured separately with its own tool registry.
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Args:
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client: The LLM client instance (AsyncOpenAI or AsyncAnthropic).
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model: The model to use.
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provider: The provider name ("openai" or "anthropic").
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include_context: Whether to include system_message and additional_messages
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in the output.
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Returns:
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A CaptureResult containing all captured tool calls.
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"""
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all_captured: list[CapturedCase] = []
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semaphore = asyncio.Semaphore(self.max_concurrent)
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async def capture_case(
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case: EvalCase,
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registry: EvalSuiteToolRegistry | None = None,
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track: str | None = None,
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) -> CapturedCase:
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"""Capture a case using the specified registry."""
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async with semaphore:
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use_registry = registry or self._internal_registry
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if use_registry is None or use_registry.tool_count() == 0:
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raise ValueError(
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"No tools registered. Use add_* convenience methods or pass catalog=ToolCatalog."
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)
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# Get tool calls based on provider
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if provider == "anthropic":
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predicted_args = await self._run_anthropic(
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client, model, case, registry=use_registry
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)
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else:
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predicted_args = await self._run_openai(
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client, model, case, registry=use_registry
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)
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# Process tool calls (resolve names, fill defaults)
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filled_actual_tool_calls = self._process_tool_calls(
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predicted_args, registry=use_registry
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)
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# Convert to CapturedToolCall objects
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tool_calls = [
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CapturedToolCall(name=name, args=args)
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for name, args in filled_actual_tool_calls
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]
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return CapturedCase(
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case_name=case.name,
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user_message=case.user_message,
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tool_calls=tool_calls,
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system_message=case.system_message if include_context else None,
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additional_messages=case.additional_messages if include_context else None,
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track_name=track,
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)
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# Capture regular cases (using default registry)
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if self.cases:
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tasks = [capture_case(case) for case in self.cases]
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regular_captured = await asyncio.gather(*tasks)
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all_captured.extend(regular_captured)
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# Capture comparative cases (each track separately)
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if self._comparative_case_builders:
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for builder in self._comparative_case_builders:
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comp_case = builder.build()
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# For each track configured in this comparative case
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for track_name in comp_case.track_configs:
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if not self._track_manager.has_track(track_name):
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continue # Skip missing tracks
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track_registry = self._track_manager.get_registry(track_name)
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# Create an EvalCase from the comparative case
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# Use case-specific rubric if defined, otherwise use suite default
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case_rubric = comp_case.rubric or self.rubric
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eval_case = self._create_eval_case(
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name=comp_case.name, # Don't embed track in name - use track_name field
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user_message=comp_case.user_message,
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system_message=comp_case.system_message,
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additional_messages=comp_case.additional_messages,
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expected_tool_calls=[], # Not needed for capture
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rubric=case_rubric,
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critics=[], # Not needed for capture
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)
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captured = await capture_case(
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eval_case, registry=track_registry, track=track_name
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)
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all_captured.append(captured)
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return CaptureResult(
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suite_name=self.name,
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model=model,
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provider=provider,
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captured_cases=list(all_captured),
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)
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