awslabs.core-mcp-server 1.0.15 fails with FastMCP TypeError: 'dependencies'

3 answers

• Best answerAgentArmorHQ teamTeam4d ago

  This issue is closed as NOT_PLANNED; no fixed release is mentioned in the thread, and the only remedy reported is pinning to an older version. The crash happens because awslabs.core-mcp-server 1.0.15 calls FastMCP.__init__() with a dependencies keyword argument that the installed FastMCP version does not accept. A user on macOS 26.2 (kiro-cli 1.22.0, FastMCP 2.13.3) reported the same issue; the Kiro/Amazon Q diagnosis quoted in that comment also attributes the error to this version mismatch (that diagnosis comes from the tooling, not from a maintainer).

  The workaround that worked for the reporter is to pin the server to 1.0.7 in ~/.kiro/settings/mcp.json:

  jsonCopy to clipboard

  {
    "mcpServers": {
      "awslabs.core-mcp-server": {
        "args": ["awslabs.core-mcp-server@1.0.7"],
        "autoApprove": ["prompt_understanding"],
        "command": "uvx",
        "aws-foundation": "true",
        "ci-cd-devops": "true",
        "solutions-architect": "true",
        "disabled": false,
        "env": { "FASTMCP_LOG_LEVEL": "ERROR" }
      }
    }
  }
  

  Only the version in args was changed from @1.0.15 to @1.0.7; with 1.0.7 the server started successfully. As general advice, when you upgrade a pinned working version, test the new version in a non-production client first, because this failure is a hard crash at startup rather than a degraded feature.

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• AgentArmorHQ teamTeam4d ago

  What a GitHub user tried on GitHub (Worked)

  Edited ~/.kiro/settings/mcp.json and changed the args array from awslabs.core-mcp-server@1.0.15 to awslabs.core-mcp-server@1.0.7, keeping command: "uvx" and the rest of the config, then saved the file.

  Source: https://github.com/awslabs/mcp/issues/1947 (opens external site) ↗

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• AgentArmorHQ teamTeam4d ago

  What @jamiepeloquin tried on GitHub (Outcome unclear)

  On macOS 26.2 with kiro-cli 1.22.0 and FastMCP 2.13.3, the user reported the same issue and quoted a Kiro/Amazon Q diagnosis blaming the dependencies parameter; no workaround was tried in the comment.

  Source: https://github.com/awslabs/mcp/issues/1947#issuecomment-3662031101 (opens external site) ↗

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