whetkit 0.3.0

Measure and improve how well LLM agents select and use the tools exposed by an MCP server

whetkit

Measure — then improve — how well LLM agents pick and use the tools your MCP server exposes.

whetkit is a local-first CLI that runs an agent against your MCP server on a set of eval tasks, scores its tool-selection hit-rate, and then curates the tool set — renaming cryptic tools, rewriting vague descriptions, pruning noise, and merging duplicates — via a reversible overlay proxy that never modifies your server. It re-runs the eval through the overlay and hands you a before/after report.

Unlike MCP inspectors and testing frameworks, whetkit closes the optimization loop: it measures agent behavior, proposes a curated tool surface, applies it through a reversible proxy, and re-runs the same evals to quantify the improvement.

whetkit doctor    ──►  ten-second lint of the tool surface        (no tasks, no API key)
whetkit inspect   ──►  what does the agent actually see?
whetkit generate  ──►  draft eval tasks from the inventory        (review, then run)
whetkit run       ──►  how often does it pick the right tools?   (hit-rate)
whetkit curate    ──►  fix the tool set, prove it helped          (before → after)

Why tool curation matters

Agents don't read your code — they read your tool names, descriptions, and schemas. A server that grew organically ends up with data_query_1, proc_ord, and do_thing: every one of them costs the model a guess, and every duplicate splits its attention. In practice a large share of agent failures on MCP servers are tool-selection failures — the model calls the wrong tool, loops through near-duplicates, or gives up — and they are fixable without touching a line of server code, because the fix is metadata. whetkit makes that loop measurable: score the failures, patch the metadata through an overlay, and show the hit-rate delta.

Install

uv tool install whetkit   # or: uvx whetkit / pipx install whetkit

(Released to PyPI from tags — see RELEASING.md. PyPI can lag behind main; the quickstart below runs from source.)

Quickstart (5 minutes)

Requires uv and an Anthropic API key (or OpenAI — see --model). Python is pinned via .python-version; uv fetches it automatically.

git clone https://github.com/benlamlih/whetkit && cd whetkit
uv sync
export ANTHROPIC_API_KEY=sk-ant-...

1. Inspect the bundled sample server — a deliberately messy e-commerce server (14 tools: cryptic names, vague descriptions, duplicates, noise):

uv run whetkit inspect --server examples/sample-server

2. Baseline eval — run 5 tasks against it and score the hit-rate (deterministic tool-matching + LLM-judge on the final answers):

uv run whetkit run --server examples/sample-server --tasks examples/tasks

3. Curate and prove it — analyze the failures, generate a curation overlay, re-run the eval through it, and get the before/after:

uv run whetkit curate --server examples/sample-server --tasks examples/tasks

This writes:

• .whetkit/curation-plan.yaml — the reviewable, hand-editable overlay plan
• .whetkit/report.html — self-contained before/after report (open it in a browser)
• .whetkit/report.json — the same data, machine-readable
• .whetkit/traces.sqlite3 — full reasoning-path traces of every run

The sample server's failures are tool-selection failures, so weaker models flip several tasks from MISS to HIT through the overlay. Frontier models often ace even the messy baseline on a 14-tool server — there the delta shows up in the other columns instead: tools exposed, tokens per task, and extra calls. On large real-world servers (dozens of tools, near-duplicates) the hit-rate delta comes back.

Stdio servers' own logs are hidden so they can't garble the output; set WHETKIT_SERVER_LOGS=1 to see them when debugging a server that won't start.

The plan is yours to edit: tweak a rename the optimizer got wrong, un-hide a tool, then re-score the curated view directly —

uv run whetkit run --server examples/sample-server --tasks examples/tasks \
  --plan .whetkit/curation-plan.yaml --group curated-v2

4. Use the curated view for real — serve it to any MCP client:

uv run whetkit overlay --server examples/sample-server --plan .whetkit/curation-plan.yaml

Nothing about your origin server changes, ever. Delete the plan and you are back to the original world.

Pointing it at your own server

• --server accepts a URL (streamable HTTP; --http-mode stateless for 2026-07-28-spec servers), a directory containing server.json or server.py, or a .py/.json path directly.
• Write tasks in YAML — format reference in docs/task-format.md — or draft them: whetkit generate --server <your-server> --out tasks/generated.yaml writes candidate tasks from the tool inventory (validated against the live tool list; review before trusting).
• --model / --judge-model / --optimizer-model take provider:model_id, e.g. anthropic:claude-sonnet-5 or openai:gpt-5.2. Keys come from ANTHROPIC_API_KEY / OPENAI_API_KEY.

Commands

Command	What it does
whetkit doctor	Lint the tool surface: vague descriptions, cryptic names, near-duplicates, context bloat. --json; --fail-on warn for CI.
whetkit inspect	Tool inventory: names, params, description tokens, schema complexity.
whetkit generate	Draft eval tasks from the inventory; validated, review-before-trust YAML.
whetkit run	Agentic eval loop with real tool execution; scored results + traces. --plan scores a curated view.
whetkit curate	Baseline → LLM-proposed overlay plan → curated eval → before/after report.
whetkit report	Rebuild the HTML/JSON report from stored traces.
whetkit overlay	Serve the curated view as a stdio MCP server.

How scoring works

• Deterministic tool-match: each task lists the expected tool calls (with acceptable alternatives, optionally ordered). Order-tolerant by default, --match-mode exact for strict grading. Reports precision/recall, missing and extra calls.
• LLM-as-judge: grades the agent's final answer against the task's natural-language success_criteria with a strict calibrated prompt; verdicts are cached in SQLite. --judge auto|on|off.
• Hit = right tools and (when judged) task success. The headline metric is the hit-rate across tasks.

More docs: docs/task-format.md · docs/curation.md · VERSIONS.md · MIGRATION.md

Development

uv sync
uv run pytest        # full suite, no API key needed (scripted fake provider)
uv run ruff check .

Dependency versions are pinned exactly and documented with sources and check dates in VERSIONS.md. The MCP transport layer supports stdio, legacy stateful streamable-HTTP (2025 spec), and stateless streamable-HTTP (2026-07-28 spec); the SDK-facing code is isolated for the v1→v2 migration (MIGRATION.md).

Scope note: whetkit is deliberately a local-first CLI. Hosting, dashboards, multi-tenancy, and security tooling are out of scope for Stage 1 — the architecture just leaves room for them.

License

Apache-2.0 — see LICENSE.