[MCP] Hosted MCP endpoint intermittently fails on fresh sessions (-32000 / -32602)

Data Access mcp
1

Hi Open Targets team,

First of all, we really appreciate the MCP offering in the first place; it’s a helpful way to work with Open Targets programmatically!

We’ve run into intermittent issues with the hosted MCP endpoint (https://mcp.platform.opentargets.org/mcp) and wanted to report them.

Using a minimal MCP client outside of Codex, we see:

  • slow connect() times (~20–30s)

  • sometimes slow listTools()

  • inconsistent behavior across repeated fresh-session runs:

    • success in some runs

    • MCP error -32000: Rate limit exceeded for client: global in others

    • MCP error -32602: Invalid request parameters during connect/init in others

We also tested the same MCP server locally with the same client and request pattern. Local runs are fast and stable, including repeated fresh-session tests and search_entities calls.

That makes us suspect this is more likely related to the hosted deployment / rate-limiting / session-init path than the server implementation itself.

Happy to share a minimal repro and logs if that would help.

Thanks!

Tobias Tilly

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Hi Tobias!

Thanks for the feedback on this. Ye, we’re struggling a bit with hard limits on Google’s Cloud Run instances.

We’ve made some changes in there, could you give it another try and report back?

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