Fix run_tool dropping empty arguments for no-arg downstream tools#3
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The run_tool handler omitted the `arguments` key entirely when the
resolved args were empty (Object.keys(...).length > 0 guard). The backend
run_tool meta-tool then forwarded a downstream tools/call with no
arguments, which serializes to null — and strict MCP servers reject it
with "Expected: object, given: null". This broke every no-argument
downstream tool (e.g. slack_read_user_profile).
Always include `arguments`, defaulting to an explicit {} when empty,
matching what the MCP SDK sends for direct tool calls. Extracted the
payload assembly into a pure buildRemoteArgs() helper and added
regression tests covering empty and populated args.
Rebuilt both shipped bundles and aligned all three plugin manifests to
0.2.18 (max prior version + mandatory version bump).
eshwar-sundar-glean
requested review from
garvit-scio and
mohit-gupta-glean
as code owners
mohit-gupta-glean
approved these changes
Jun 13, 2026
| { | ||
| "name": "glean-experimental", | ||
| "version": "0.2.17", | ||
| "version": "0.2.18", |
There was a problem hiding this comment.
#suggestion, in a separate PR, can we add a check to make sure that the 3 versions remain in sync.
| throw err; | ||
| } | ||
| const remoteArgs = { | ||
| return callRemoteTool( |
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Problem
run_toolfailed for every downstream tool called with no arguments (e.g.slack_read_user_profile), returning:Root cause
In
src/tools/run-tool.ts, the payload assembly omitted theargumentskey entirely when the resolved args were empty:With the key absent, the backend
run_toolmeta-tool forwarded a downstreamtools/callwith noarguments, which serializes tonull. Strict downstream MCP servers validateparams.argumentsas an object and rejectnull.The key's presence, not its value, was the only difference between a failing and succeeding call — passing any non-empty object (the prior workaround) incidentally tripped the guard true.
Fix
Always include
arguments, defaulting to an explicit{}when empty — matching what the MCP SDK sends for direct tool calls. Extracted the assembly into a purebuildRemoteArgs()helper and added regression tests for the empty and populated cases.Verification
npm run typecheck— cleannpm test— 134 passed, including 2 newbuildRemoteArgstests