MCP Server Framework and Tool Development library for building custom capabilities into agents.
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Evan Tahler 0fc9e21308
Improve error messages with fix instructions (#713)
Improve user-facing error messages to provide actionable fix
instructions, enhancing developer experience and reducing support
queries.

---
Linear Issue:
[TOO-199](https://linear.app/arcadedev/issue/TOO-199/audit-error-messages-for-actionable-fix-instructions)

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<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Enhances MCP server/session error responses with clear, actionable
guidance across JSON-RPC, tools, and resources; updates tests to assert
new messages.
> 
> - **Server (`arcade_mcp_server/server.py`)**
> - **Actionable JSON-RPC errors**: Rich messages for `Invalid request`,
`Not initialized`, `Method not found`, and internal errors with
troubleshooting steps.
>   - **Tools**:
> - `tools/list`/`tools/call`: Improved internal error messages;
user-facing guidance on failures.
>     - Unknown tool: returns detailed fix instructions.
> - Transport restrictions: explicit "Unsupported transport" guidance
for HTTP vs `stdio` with docs link.
> - Auth flow: messages for missing API key, pending authorization (with
`authorization_url`), and authorization errors; includes next steps.
> - Secrets: clear "Missing secret(s)" with `.env`/env-var setup
instructions.
>   - **Resources/Prompts**:
> - `resources/list`, `resources/templates/list`, `resources/read`,
`prompts/list`, `prompts/get`: Detailed failure and not-found messages
with guidance.
> - **Session (`arcade_mcp_server/session.py`)**
> - Enhanced internal error response formatting with troubleshooting
steps.
> - **Tests (`libs/tests/arcade_mcp_server/test_server.py`)**
> - Updated assertions to match new, descriptive messages (e.g.,
"Authorization required", "Missing Arcade API key", "Unsupported
transport").
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
97a6db4ec80a1ea9597f3364b6325d47948c94e0. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

---------

Co-authored-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: Eric Gustin <34000337+EricGustin@users.noreply.github.com>
2025-12-10 10:16:38 -08:00
.cursor/rules Cursor versioning rules (#715) 2025-12-09 11:31:15 -08:00
.github Update release-on-version-change.yml (#671) 2025-11-03 11:55:56 -08:00
.vscode Rename some 'toolkit' references to 'server' (#624) 2025-10-14 18:42:27 -07:00
contrib Bumps critical JS dependency versions (#699) 2025-12-01 18:38:22 -08:00
docker Remove all Starter MCP Servers migrated to the starter-tools repo (#710) 2025-12-03 22:12:06 -03:00
examples Rename example servers (#675) 2025-11-12 10:21:25 -08:00
libs Improve error messages with fix instructions (#713) 2025-12-10 10:16:38 -08:00
schemas/preview Tool Metadata (#357) 2025-04-16 19:17:36 -08:00
toolkits Remove all Starter MCP Servers migrated to the starter-tools repo (#710) 2025-12-03 22:12:06 -03:00
.editorconfig Fix ruff (#64) 2024-09-25 09:47:30 -07:00
.gitignore Re-import arcade_core errors into arcade_mcp_server (#620) 2025-10-13 17:48:54 -07:00
.pre-commit-config.yaml MCP Local (#563) 2025-09-25 15:28:15 -07:00
.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 MCP Local (#563) 2025-09-25 15:28:15 -07:00
CONTRIBUTING.md Rename some 'toolkit' references to 'server' (#624) 2025-10-14 18:42:27 -07:00
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 Rename _meta requirements field to arcade_requirements (#616) 2025-10-14 19:01:05 -07:00
pyproject.toml Improve message when evals isn't installed (#687) 2025-12-09 15:41:15 -08:00
README.md Fix MCP capabilities, examples, tests, and more (#657) 2025-10-30 11:59:00 -07:00
SECURITY.md Create SECURITY.md (#693) 2025-11-24 18:14:40 -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

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