The enabledTools allowlist was only enforced for MCP tools returned by
session.list_tools(). Resources and prompts from session.list_resources()
and session.list_prompts() were registered unconditionally, allowing a
deny-all or restrictive enabledTools config to leak resource and prompt
capabilities to the model.
Now resources and prompts are only registered when allow_all_tools is
true (default ["*"] wildcard). Any explicit tool restriction — including
enabledTools: [] (deny-all) or a list of specific tool names — also
blocks resource and prompt registration from that server.
Fixes#4435
Maintainer edit: make the unsafe redirect regression go through connect_mcp_servers so both SSE and streamable HTTP prove that the request hook is attached to the MCP clients before redirects are followed.
MCP resource/prompt/tool names containing spaces or special characters
(e.g. "PostgreSQL System Information") were forwarded verbatim to model
provider APIs, causing validation errors from both Anthropic and OpenAI
which require names matching ^[a-zA-Z0-9_-]{1,128}$.
Add _sanitize_name() that replaces invalid characters with underscores
and collapses consecutive underscores. Applied in MCPToolWrapper,
MCPResourceWrapper, MCPPromptWrapper constructors and the enabled_tools
filtering logic.
Closes#3468
Each MCP server now connects in its own asyncio.Task to isolate anyio
cancel scopes and prevent 'exit cancel scope in different task' errors
when multiple servers (especially mixed transport types) are configured.
Changes:
- connect_mcp_servers() returns dict[str, AsyncExitStack] instead of None
- Each server runs in separate task via asyncio.gather()
- AgentLoop uses _mcp_stacks dict to track per-server stacks
- Tests updated to handle new API
- Propagate `description` from MCP prompt arguments into the JSON
Schema so LLMs can better understand prompt parameters.
- Align generic-exception error message with tool/resource wrappers
(drop redundant `{exc}` detail).
- Extend test fixture to mock `mcp.shared.exceptions.McpError`.
- Add tests for argument description forwarding and McpError handling.
Made-with: Cursor
Add MCPResourceWrapper and MCPPromptWrapper classes that expose MCP
server resources and prompts as nanobot tools. Resources are read-only
tools that fetch content by URI, and prompts are read-only tools that
return filled prompt templates with optional arguments.
- MCPResourceWrapper: reads resource content (text and binary) via URI
- MCPPromptWrapper: gets prompt templates with typed arguments
- Both handle timeouts, cancellation, and MCP SDK 1.x error types
- Resources and prompts are registered during server connection
- Gracefully handles servers that don't support resources/prompts
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