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

Annotations already declare read-only, idempotent, and non-destructive behavior, but the description adds valuable details beyond them: the 400-line diff cap, the error contract (never raises protocol errors; returns a structured error object), example output shape, and retry safety. These additions help the agent predict behavior and handle failures.

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 purpose is front-loaded and the structure is logical. However, 'FREE.' is marketing noise, and the explicit 'read-only and idempotent' sentence redundantly repeats annotation hints, adding slight bloat without new value.

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?

For a simple two-parameter diff tool with a rich schema, full annotations, and an output schema, the description covers purpose, usage, return shape, limits, error behavior, and safety. Nothing an agent needs to invoke it correctly is missing.

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 and maxLength constraints for both parameters. The description gives a typical input example ('a': old text, 'b': new text) but adds no semantic detail beyond what the schema already provides. Baseline 3 is appropriate when the schema does the heavy lifting.

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 opens with a specific verb and resource: 'Produce a unified diff between two texts.' It also contextualizes the use case ('comparing two SKILL.md versions') and explicitly distinguishes the tool from risk-judging alternatives. No sibling tool overlaps in function, so the agent can identify it unambiguously.

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?

It states clear when-to-use guidance ('Use to show exactly what changed between two versions of a text') and explicit exclusions ('Not for judging the risk of a code change - the codereview server's review_diff does that'). This routes the agent correctly without inference.

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