tool-evaluation

A set of rules for improving developer tools through prototypes, measured tests, transcript review, and repeated refinement. An evaluation checks whether a tool helps an agent complete a task correctly.

In plain words
What is it for?
Use it to design and test MCP servers or other agent tools, create realistic test tasks, inspect failures, and compare improvements on separate test cases.
Why use it?
It replaces guesswork with evidence about where tools fail, confuse agents, or produce unreliable results.

Cursor rule for Cursor

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add rules/sijeeshmiziha/visionagent/tool-evaluation
Clone the repo
git clone --depth 1 https://github.com/sijeeshmiziha/visionagent

Made for: Cursor.

Per session 395 This file is loaded in full into every session.
When invoked 395 The same file — it is already loaded in full.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00395 $0.00395
Opus 5 $0.00198 $0.00198
Sonnet 5 $0.00079 $0.00079
Haiku 4.5 $0.00040 $0.00040

Measured 2d ago against content hash 8ee0d3fa7fdd, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

tool-evaluation scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.cursor/rules/tool-evaluation.mdc · 35 lines

What it actually says

Tool Evaluation and Improvement

Mindset

  • Tools are contracts between deterministic systems and non-deterministic agents; design for agents, not just for APIs.
  • Use evaluation to measure and improve tool effectiveness.

Process

  1. Prototype: Build a quick prototype (e.g. MCP server or tools passed into the API); test locally and collect user feedback.
  2. Evaluate: Run a programmatic evaluation—one agentic loop per task, each with a single task prompt and your tools.
  3. Analyze: Read transcripts and reasoning; identify where agents get stuck or misuse tools.
  4. Collaborate: Feed evaluation transcripts into an agent (e.g. Claude Code) to refactor tools and descriptions; use a held-out test set to avoid overfitting.

Evaluation Tasks

  • Ground tasks in real-world use; prefer multi-step, multi-tool scenarios over trivial sandbox prompts.
  • Pair each prompt with a verifiable outcome (exact match or LLM-as-judge). Avoid verifiers that reject correct answers due to formatting or phrasing.
  • In evaluation system prompts, ask agents to output reasoning or feedback blocks (or use extended thinking) to diagnose why tools are or aren’t used.

Metrics

  • Track accuracy plus: tool-call count, token consumption, tool errors, runtime.
  • Redundant tool calls may suggest pagination or token limits; many invalid-parameter errors may suggest clearer descriptions or examples.

Analysis

  • Read evaluation agents’ reasoning and raw transcripts (including tool calls and responses); “read between the lines”—agents don’t always say what they mean.
  • Use metrics to spot improvement areas: e.g. rightsizing pagination, clarifying parameter descriptions, consolidating common workflows.
Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 35 lines · 395 tokens per session scan A 8ee0d3fa7fdd

Subscribe to this mod's changes

tool-evaluation is a cursor rule published in the GitHub repository sijeeshmiziha/visionagent (2 stars, last pushed 5mo ago), licensed MIT. It adds 395 tokens to every session, about $0.0020 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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