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

Although annotations already declare readOnlyHint and openWorldHint, the description adds substantial context beyond them: no authentication required, ~25s first-request latency, a 'pending' status with retry_after_s and retry guidance, the types-only analysis method, and the blind spot for non-type behavior changes. It also describes the return shape (summary with counts and likely_breaking flag plus before/after detail).

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?

Front-loaded with the core action and method, then output shape, operational traits, limits, and finally alternatives. Every sentence carries distinct, load-bearing information with no filler despite the length.

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?

No output schema exists, yet the description explains the return contents (summary counts, likely_breaking flag, per-change before/after), the pending/retry flow, scope limits, and unsupported registries. An agent has everything needed to call and interpret it correctly.

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%, so 'from' and 'to' formats and the newer-than constraint are fully documented in the schema. The description adds the version-pair pairing concept but no syntax the schema lacks, so the baseline 3 applies.

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 states a precise verb and resource ('Reports what changes between two versions of an npm package by diffing the public TypeScript API') and enumerates exactly what is diffed (exports, import paths, signatures, members, deprecations, engines/peerDependencies, changelog). This is immediately distinguishable from sibling tools like symbol_status or version_status.

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 gives explicit use cases ('BEFORE upgrading a dependency across a major version, or when code written for an old version fails on a new one') and routes three alternative scenarios to named siblings: symbol_status for one API in one version, version_status for vulnerabilities, find_compatible_version for runtime fit.

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