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

The annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false. The description goes well beyond by specifying that errors are never protocol errors but structured JSON, providing exact error examples, stating the diff cap (400 lines), describing the output format for identical inputs, and confirming read-only/idempotent nature. 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 well-structured: purpose first, then usage guidance, then error handling, then safety note. All sentences serve a purpose. Slight verbosity in the error example and the 'FREE.' label could be trimmed, but overall it is efficient and front-loaded.

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?

Given the tool's simplicity (2 params, no enums, output schema exists but not shown), the description fully covers input format, output format (both normal and error), limits (400 diff lines, 500000 char text), and behavioral properties (read-only, idempotent, retry safety). No significant gaps.

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 description coverage is 100%, with clear parameter descriptions already in the schema. The description adds a typical input example ({a, b}) and reaffirms the character limit in an error example, but these are supplementary rather than essential. Baseline of 3 is appropriate as 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-resource pairing: 'Produce a unified diff between two texts.' It clearly distinguishes itself from a related tool (review_diff) that judges risk of code changes. Among the listed siblings, it is the only text comparison tool, making its purpose unmistakable.

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?

The description explicitly states when to use ('show exactly what changed between two versions of a text'), when not to use ('not for judging the risk of a code change'), and provides an explicit alternative ('the codereview server's review_diff does that'). It also gives example input and explains retry safety, leaving no ambiguity.

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