feat(mcp): add allowedTools filtering support to OneMcpServer

[chkuang-g]

Description

Adds support for tool filtering in OneMcpServer via an optional allowedTools?: string[] parameter in OneMcpServerOptions (addressing b/535744232).

• listTools() filters remote tool list responses against allowedTools.
• callTool() guards against invoking tools not present in allowedTools.

Scenarios Tested

• Unit tests in src/mcp/onemcp/onemcp_server.spec.ts verifying listTools filters tools when allowedTools is configured.
• Unit tests in src/mcp/onemcp/onemcp_server.spec.ts verifying callTool throws a FirebaseError for unallowed tools.
• Unit tests verifying backward compatibility when allowedTools is omitted or empty.

Sample Commands

npx mocha --require ts-node/register src/mcp/onemcp/onemcp_server.spec.ts

[gemini-code-assist]

Code Review

This pull request introduces tool filtering support to OneMcpServer via a new allowedTools configuration option, filtering the tools returned by listTools() and checking permissions in callTool(). The review feedback points out that callTool() currently only logs a warning when a disallowed tool is invoked instead of blocking execution. To properly guard the execution and adhere to the repository style guide, the reviewer recommends throwing a FirebaseError when a disallowed tool is called, and updating the corresponding unit tests to assert this error behavior.

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src/mcp/onemcp/onemcp_server.ts (120-128)

The implementation currently only logs a warning when a disallowed tool is called, and then proceeds to execute the tool anyway. According to the PR description, callTool() is supposed to guard against invoking tools not present in allowedTools. To properly guard and prevent execution, we should throw a FirebaseError as specified in the repository style guide for expected, user-facing errors.

    if (
      this.options.allowedTools?.length &&
      !this.options.allowedTools.includes(toolName) &&
      !this.options.allowedTools.includes(this.feature + "_" + toolName)
    ) {
      throw new FirebaseError(
        "Tool '" + toolName + "' is not allowed on remote server for feature '" + this.feature + "'."
      );
    }

References

1. Throw FirebaseError (src/error.ts) for expected, user-facing errors. ^(link)

src/mcp/onemcp/onemcp_server.spec.ts (234-252)

Since callTool should throw a FirebaseError when a disallowed tool is called, this test should be updated to assert that the promise is rejected with a FirebaseError instead of checking for a logged warning.

    it("should throw FirebaseError when calling a tool not in allowedTools", async () => {
      const serverWithFilter = new OneMcpServer(
        feature,
        serverUrl,
        { requiresAuth: false, requiresProject: true },
        { allowedTools: ["allowed_tool"] },
      );

      const fn = (serverWithFilter as any).callTool.bind(serverWithFilter);
      await expect(fn("disallowed_tool", {}, mockContext)).to.be.rejectedWith(
        FirebaseError,
        /is not allowed on remote server/
      );
    });

[joehan]

Omit the CHANGELOG for this one - its not a user facing change, but rather an implementation detail

[joehan]

LGTM, just remove the changelog