MCP Server Framework and Tool Development library for building custom capabilities into agents.
Find a file
Francisco Or Something 8f5d0ff54e
Improve typed httpx error mapping and adapter guidance (#820)
## Summary

Routes HTTP adapter exceptions to the right error class instead of
shoe-horning everything into `UpstreamError`. Addresses Eric's earlier
feedback that several exceptions this PR was wrapping as `UpstreamError`
didn't satisfy the "something happened with the upstream" claim (local
pool exhaustion, client-side request construction, local TLS failures).

### Scope

- `UpstreamError` (unchanged) — upstream responded with an HTTP status
code.
- **`NetworkTransportError`** (new sibling in `arcade-core`) — no
complete response was received. `status_code=None`. Three kinds:
`NETWORK_TRANSPORT_RUNTIME_TIMEOUT`, `_UNREACHABLE`, `_UNMAPPED`.
- **`FatalToolError`** (existing) — client construction bugs
(`InvalidURL`, `UnsupportedProtocol`, `MissingSchema`, `InvalidHeader`,
`LocalProtocolError`, …) and local TLS/cert config failures. Never
retried.

---

## Before / After (per Eric's request)

Shows the error payload a tool produces for each exception, before this
PR vs. after. "Before" = current `main` (exceptions without real HTTP
responses fall through to the generic `@tool` `FatalToolError` catch-all
with `message=str(exc)`).

### No-response transport failures

| Exception | Before — class / message / kind | After — class / message
/ kind |
|---|---|---|
| `httpx.PoolTimeout` | `FatalToolError` — `str(exc)` leaks raw detail —
`TOOL_RUNTIME_FATAL`, not retryable | `NetworkTransportError` — `"HTTP
request timed out before a complete response was received."` —
`NETWORK_TRANSPORT_RUNTIME_TIMEOUT`, **retryable** |
| `httpx.ConnectTimeout` | same as above | same as PoolTimeout —
`TIMEOUT`, retryable |
| `httpx.ConnectError` (refused / DNS) | `FatalToolError` — `str(exc)` |
`NetworkTransportError` — `"HTTP request failed before reaching the
upstream service."` — `UNREACHABLE`, retryable |
| `httpx.RemoteProtocolError` (upstream sent bad HTTP) |
`FatalToolError` — `str(exc)` | `NetworkTransportError` — same message
as ConnectError — `UNREACHABLE`, retryable |
| `httpx.DecodingError` | `FatalToolError` — `str(exc)` |
`NetworkTransportError` — `"HTTP response from upstream could not be
decoded."` — `UNMAPPED`, retryable |
| `httpx.TooManyRedirects` | `FatalToolError` — `str(exc)` |
`NetworkTransportError` — `"HTTP redirect limit exceeded before a final
response was received."` — `UNMAPPED`, **not** retryable |

### Client construction / local env bugs

| Exception | Before | After |
|---|---|---|
| `httpx.UnsupportedProtocol`, `httpx.InvalidURL`,
`httpx.LocalProtocolError` | `FatalToolError` with `message=str(exc)`
(may leak scheme / URL content) | `FatalToolError` — `"Tool constructed
an invalid HTTP request — likely a tool-authoring bug."` —
`TOOL_RUNTIME_FATAL`, not retryable |
| `requests.MissingSchema`, `InvalidURL`, `InvalidHeader`,
`InvalidSchema`, `InvalidProxyURL`, `URLRequired` | same as above | same
as above |
| `requests.SSLError` | `FatalToolError` — `str(exc)` often contains raw
cert chain detail | `FatalToolError` — `"TLS handshake failed — likely a
local certificate or trust configuration issue."` —
`TOOL_RUNTIME_FATAL`, not retryable |

### Real HTTP response errors (UNCHANGED — same behavior)

| Exception | Class | Message | Kind | Retryable |
|---|---|---|---|---|
| `httpx.HTTPStatusError` 404 | `UpstreamError` | `"Upstream HTTP
request failed (Not Found, client error)."` |
`UPSTREAM_RUNTIME_NOT_FOUND` | No |
| `httpx.HTTPStatusError` 429 (w/ Retry-After: 60) |
`UpstreamRateLimitError` | `"Upstream HTTP request failed (Too Many
Requests, client error). Retry after 60 second(s)."` |
`UPSTREAM_RUNTIME_RATE_LIMIT` | Yes |
| `httpx.HTTPStatusError` 500 | `UpstreamError` | `"Upstream HTTP
request failed (Internal Server Error, server error)."` |
`UPSTREAM_RUNTIME_SERVER_ERROR` | Yes |

### What's no longer in the message

- Raw exception `str(exc)` output (which frequently includes the full
URL with query-string tokens, connection pool details, or cert chains)
is **no longer the agent-facing `message`**. It's preserved in
`developer_message` for server-side diagnostics.
- The misleading "Upstream HTTP…" prefix is gone from network-transport
and construction-bug messages. Those messages now honestly describe what
happened on the tool side.
- For 429s without a `Retry-After` header, we still show "Retry after N
seconds." (pre-existing behavior; see follow-up notes).

---

## Companion PRs

-
[ArcadeAI/arcade-mcp#823](https://github.com/ArcadeAI/arcade-mcp/pull/823)
— introduces `NetworkTransportError` in `arcade-core`
- [ArcadeAI/monorepo#911](https://github.com/ArcadeAI/monorepo/pull/911)
— adds the 3 `ErrorKind` constants to the Go engine and Datadog
dashboards
- [ArcadeAI/docs#920](https://github.com/ArcadeAI/docs/pull/920) —
documents the new hierarchy and adapter routing

## Follow-ups (out of scope for this PR)

A short investigation surfaced several pre-existing issues that are
worth fixing separately. A full list is in
`NETWORK_TRANSPORT_ERROR_FOLLOWUPS.md` (shared offline). Summary:

1. `requests.HTTPError` with `response is None` returns `None` from the
adapter; should fall through to the `NetworkTransportError(UNMAPPED)`
fallback instead of becoming a generic `FatalToolError`.
2. `developer_message` can leak URL query strings (and therefore tokens)
since it stores raw `str(exc)`.
3. `_sanitize_uri` does not strip userinfo (credentials in URL path).
4. `_parse_retry_ms` misinterprets epoch-style `x-ratelimit-reset`
headers.
5. 429 responses without `Retry-After` synthesize a fabricated "Retry
after 1 second(s)." suffix.
6. `UPSTREAM_RUNTIME_VALIDATION_ERROR` is defined but never emitted.
7. `UpstreamError` silently accepts out-of-range status codes.
8. `requests.HTTPError` branch re-extracts `request_url` /
`request_method` inconsistently (dead work).

## Test plan

- [x] Existing `libs/tests/sdk/test_httpx_adapter.py` +
`test_graphql_adapter.py` updated; every no-response / construction-bug
test asserts the new class + kind + `can_retry`.
- [x] Full test suite passes locally.
- [x] mypy clean on `arcade-core`, `arcade-tdk`, `arcade-mcp-server`.
- [x] Smoke-tested 21 exception routing cases end-to-end against real
httpx / requests exceptions.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Medium Risk**
> Changes core error classification and retryability for
`httpx`/`requests`/GraphQL transport failures, which can affect tool
retry behavior and telemetry. Risk is mitigated by extensive new/updated
tests covering the new mappings and privacy expectations.
> 
> **Overview**
> **Improves error adapter behavior to be more semantically correct and
privacy-safe.** The HTTP adapter now distinguishes real HTTP responses
(`UpstreamError`/`UpstreamRateLimitError`) from no-response failures
(`NetworkTransportError` with `ErrorKind` + retryability) and from
client construction/local TLS issues (`FatalToolError`).
> 
> **Reduces sensitive data exposure in agent-facing messages.**
Status-based errors now emit standardized messages derived from status
phrase/class, while preserving raw exception detail in
`developer_message`; Google/Microsoft/Slack fallback paths similarly
switch to `unhandled <ExceptionType>` messages and move `str(exc)` into
`developer_message`. GraphQL transport connection/protocol errors are
reclassified from `UpstreamError` (502) to `NetworkTransportError`, and
transport/server messages are standardized.
> 
> Bumps `arcade-tdk` version to `3.8.0` and expands/updates the SDK test
suite to assert new classes, `kind`, `can_retry`, request metadata
extraction, and privacy behavior.
> 
> <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit
1041cb1bec4fa3b0bae3e7c6b860b84cf376cf9a. Bugbot is set up for automated
code reviews on this repo. Configure
[here](https://www.cursor.com/dashboard/bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
2026-04-20 20:32:17 -03:00
.claude/skills/build-error-adapter Improve typed httpx error mapping and adapter guidance (#820) 2026-04-20 20:32:17 -03:00
.cursor/rules Cursor versioning rules (#715) 2025-12-09 11:31:15 -08:00
.github Add state github bot (#812) 2026-04-07 17:48:06 -07:00
.vscode Rename some 'toolkit' references to 'server' (#624) 2025-10-14 18:42:27 -07:00
examples Don't return structuredContent when error (#817) 2026-04-10 15:27:07 -07:00
libs Improve typed httpx error mapping and adapter guidance (#820) 2026-04-20 20:32:17 -03:00
schemas/preview Tool Metadata (#357) 2025-04-16 19:17:36 -08:00
tests Improve .env discovery (#737) 2026-02-25 23:20:28 -08:00
.editorconfig Fix ruff (#64) 2024-09-25 09:47:30 -07:00
.gitignore feat: Add TelemetryPassbackMiddleware for serverExecutionTelemetry capability (#797) 2026-03-25 15:57:50 -07:00
.pre-commit-config.yaml Left over fixes for Windows Papercut PR (#781) 2026-02-26 13:24:15 -03:00
.prettierignore Fix ruff (#64) 2024-09-25 09:47:30 -07:00
.prettierrc.toml Fix ruff (#64) 2024-09-25 09:47:30 -07:00
.ruff.toml [TOO-522] Supress chardet noizy versioning warning (#792) 2026-03-13 15:56:15 -07:00
CLAUDE.md Update CLAUDE.md (#815) 2026-04-08 16:49:58 -07:00
CONTRIBUTING.md [TOO-326] Windows papercuts (#768) 2026-02-25 13:18:16 -03:00
cspell.config.yaml Replace arcade.client with arcadepy (#119) 2024-10-23 15:29:02 -07:00
LICENSE Update README and LICENSE (#220) 2025-01-23 19:43:48 -08:00
Makefile Remove toolkits (#784) 2026-02-26 09:09:46 -08:00
pyproject.toml feat: added connect cli command (#819) 2026-04-15 13:16:50 -07:00
README.md Fix broken links (#738) 2026-01-05 13:27:16 -08:00
SECURITY.md Fix broken links (#738) 2026-01-05 13:27:16 -08:00
uv_setup.sh MCP Local (#563) 2025-09-25 15:28:15 -07:00

Prebuilt ToolsContact Us

Arcade MCP Server Framework

  • To see example servers built with Arcade MCP Server Framework (this repo), check out our examples

  • To learn more about the Arcade MCP Server Framework (this repo), check out our Arcade MCP documentation

  • To learn more about other offerings from Arcade.dev, check out our documentation.

Pst. hey, you, give us a star if you like it!

GitHub stars

Quick Start: Create a New Server

The fastest way to get started is with the arcade new CLI command, which creates a complete MCP server project:

# Install the CLI
uv tool install arcade-mcp

# Create a new server project
arcade new my_server

# Navigate to the project
cd my_server/src/my_server

This generates a project with:

  • server.py - Main server file with MCPApp and example tools

  • pyproject.toml - Dependencies and project configuration

  • .env.example - Example .env file containing a secret required by one of the generated tools in server.py

The generated server.py includes proper command-line argument handling and three example tools:

#!/usr/bin/env python3
"""simple_server MCP server"""

import sys
from typing import Annotated

import httpx
from arcade_mcp_server import Context, MCPApp
from arcade_mcp_server.auth import Reddit

app = MCPApp(name="simple_server", version="1.0.0", log_level="DEBUG")


@app.tool
def greet(name: Annotated[str, "The name of the person to greet"]) -> str:
    """Greet a person by name."""
    return f"Hello, {name}!"


# To use this tool locally, you need to either set the secret in the .env file or as an environment variable
@app.tool(requires_secrets=["MY_SECRET_KEY"])
def whisper_secret(context: Context) -> Annotated[str, "The last 4 characters of the secret"]:
    """Reveal the last 4 characters of a secret"""
    # Secrets are injected into the context at runtime.
    # LLMs and MCP clients cannot see or access your secrets
    # You can define secrets in a .env file.
    try:
        secret = context.get_secret("MY_SECRET_KEY")
    except Exception as e:
        return str(e)

    return "The last 4 characters of the secret are: " + secret[-4:]

# To use this tool locally, you need to install the Arcade CLI (uv tool install arcade-mcp)
# and then run 'arcade login' to authenticate.
@app.tool(requires_auth=Reddit(scopes=["read"]))
async def get_posts_in_subreddit(
    context: Context, subreddit: Annotated[str, "The name of the subreddit"]
) -> dict:
    """Get posts from a specific subreddit"""
    # Normalize the subreddit name
    subreddit = subreddit.lower().replace("r/", "").replace(" ", "")

    # Prepare the httpx request
    # OAuth token is injected into the context at runtime.
    # LLMs and MCP clients cannot see or access your OAuth tokens.
    oauth_token = context.get_auth_token_or_empty()
    headers = {
        "Authorization": f"Bearer {oauth_token}",
        "User-Agent": "{{ toolkit_name }}-mcp-server",
    }
    params = {"limit": 5}
    url = f"https://oauth.reddit.com/r/{subreddit}/hot"

    # Make the request
    async with httpx.AsyncClient() as client:
        response = await client.get(url, headers=headers, params=params)
        response.raise_for_status()

        # Return the response
        return response.json()

# Run with specific transport
if __name__ == "__main__":
    # Get transport from command line argument, default to "stdio"
    # - "stdio" (default): Standard I/O for Claude Desktop, CLI tools, etc.
    #   Supports tools that require_auth or require_secrets out-of-the-box
    # - "http": HTTPS streaming for Cursor, VS Code, etc.
    #   Does not support tools that require_auth or require_secrets unless the server is deployed
    #   using 'arcade deploy' or added in the Arcade Developer Dashboard with 'Arcade' server type
    transport = sys.argv[1] if len(sys.argv) > 1 else "stdio"

    # Run the server
    app.run(transport=transport, host="127.0.0.1", port=8000)

This approach gives you:

  • Complete Project Setup - Everything you need in one command

  • Best Practices - Proper dependency management with pyproject.toml

  • Example Code - Learn from working examples of common patterns

  • Production Ready - Structured for growth and deployment

Running Your Server

Run your server directly with Python:

# Run with stdio transport (default)
uv run server.py

# Run with http transport via command line argument
uv run server.py http

# Or use python directly
python server.py http
python server.py stdio

Your server will start and listen for connections. With HTTP transport, you can access the API docs at http://127.0.0.1:8000/docs.

Configure MCP Clients

Once your server is running, connect it to your favorite AI assistant:

arcade configure claude # Configure Claude Desktop to connect to your stdio server in your current directory
arcade configure cursor --transport http --port 8080 # Configure Cursor to connect to your local HTTP server on port 8080
arcade configure vscode --entrypoint my_server.py # Configure VSCode to connect to your stdio server that will run when my_server.py is executed directly

Installing this Repo from Source

git clone https://github.com/ArcadeAI/arcade-mcp.git && cd arcade-mcp && make install

Support and Community