improvement(search): return 30 previews by default for a Search MCP query across every source

[waleedlatif1]

Summary

• Search MCP: a query across every source (no source, nativeQueries, or date sortBy) that sets no topK now returns up to 30 previews instead of 20. Single-source searches, native queries, and date-sorted listings keep 20; an explicit topK is unchanged
• A federated search shares one list among every connected source, so at 20 the passage that answers the question was often cut; at 30 the assistant gets it without a follow-up search
• Split the assistant search input into its fields and an exported refinement so the MCP schema can make topK optional (the MCP SDK applies schema defaults before the handler, and zod 4 can't make a field optional on a refined schema). The assistant tool's generated catalog is byte-identical
• Search tab and the Sim assistant tool are unchanged

Type of Change

• Improvement

Testing

• Two interleaved A/B runs of a 12-question assistant benchmark against live sources through a proxy reproducing the server merge, judged per answer: overall +2.9 [95% CI +1.1, +4.6] and +1.0 [−0.6, +2.5]; correctness +4.2 / +1.9, completeness +4.4 / +1.8. The two hardest questions improved 11–15 points in both runs; no question regressed by more than 5. Cost: about 2 s more and ~25% more input tokens per answer
• New server.test.ts cases cover the default per search shape, and server.protocol.test.ts checks it through the real MCP SDK; both fail on the previous code
• vitest on lib/knowledge/mcp, mothership-assistant-tools.test.ts, lib/mothership/tools/server/knowledge (68 passed); mship-tools:generate output identical before/after; biome lint

Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing (new tests pass the test-audit authoring gate)
• No new warnings introduced
• I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)

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1 Skipped Deployment

Project	Deployment	Actions	Updated
docs	Skipped		Oct 20, 2026 7:53am UTC

[greptile-apps]

Confidence Score: 5/5

[Medium impact] The PR appears safe to merge.

Summary

Search MCP now defaults to 30 previews for cross-source text searches, including explicit sortBy: 'relevance'. Scoped searches, native queries, and date-sorted listings keep 20; explicit topK stays unchanged.

• Search MCP returns more previews for plain searches across every source.

_{Reviews (2) · Last reviewed commit: "improvement(search): treat relevance sor..." · Reviewed by Greptile}

[cubic-dev-ai]

All reported issues were addressed across 4 files

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[waleedlatif1]

@greptile

[waleedlatif1]

@cubic-dev-ai review this PR

[cubic-dev-ai]

@cubic-dev-ai review this PR

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[cubic-dev-ai]

No issues found across 5 files

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

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