maintainer edit: keep MCP HTTP SSRF checks strict, pin validated DNS for direct web_fetch and HTTP/SSE MCP requests, preserve explicit and environment proxy compatibility, and cover the proxy/redirect/rebinding cases with tests.
maintainer edit: update the existing transient retry tests for reconnect-first behavior and keep structured retry-failure coverage in the focused MCP transient suite.
maintainer edit: treat transient MCP stream failures as dead sessions so the existing reconnect handler can refresh the session before retrying. Also cover retry failure as a structured tool error.
MCP server URLs can carry secrets in userinfo
(`https://user:token@host/sse`) or a query string (`?token=...`). A few
connect/validate paths logged the raw `cfg.url` / `request.url`, so those
secrets could land in log files that are often shared or aggregated.
Add a small `_redact_url()` helper that keeps only scheme/host/port/path
and use it at the four sites that log a server or request URL. Logging
only; no other behavior changes.
MCPToolWrapper.execute only handled TextContent; every other block was
rendered with str(block). An MCP ImageContent block therefore became a
large base64 string embedded in the tool result, which (a) was truncated
by max_tool_result_chars, corrupting the data, and (b) could never reach a
channel because it was plain text, not an image artifact.
Decode ImageContent (and EmbeddedResource blobs with an image/* MIME type)
and persist them via store_generated_image_artifact, returning the same
compact {artifacts, next_step} JSON the built-in image_generation tool
produces. The base64 stays out of the model context; the model delivers the
saved file via the message tool's media parameter.
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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