Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint. The description reinforces these and adds important behaviors: diff capped at 400 lines, specific error response format without protocol errors, and the retry guarantee. No contradictions.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single coherent paragraph that front-loads the core purpose, then logically covers usage, an example return, limits, alternative tool, and error handling. Every sentence serves a purpose, though it could be slightly more compact without losing information.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With a fully described input schema, an output schema present, detailed annotations, and a description covering behavioral cap, error format, and retry safety, the tool is well-specified. Minor omissions (e.g., what happens if diff exceeds 400 lines) keep it from a 5.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% with clear descriptions for each parameter. The description adds value by providing a typical input example ({'a': '<old text>', 'b': '<new text>'}) and confirming the maxLength constraint, which helps the agent understand usage beyond the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states 'Produce a unified diff between two texts' with a specific verb and resource. It distinguishes itself from sibling tools (validation utilities) by being a diff tool, and the 'FREE' note adds helpful context. No ambiguity.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explicitly provides a concrete use case ('comparing two SKILL.md versions') and an explicit exclusion: 'Not for judging the risk of a code change - the codereview server's review_diff does that.' Also explains error handling and retry safety, guiding correct invocation.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.