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

Annotations already declare the operation as read-only, idempotent, and non-destructive, so the description does not need to restate those. It adds useful context about what kinds of breaking changes are reported and that migration guides are included, while avoiding any contradiction with the annotations.

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 two sentences with no filler. The core purpose and output categories are front-loaded, and the alternative-tool guidance is a useful second sentence.

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?

The description is largely complete given the annotations and output schema. The main gap is that both version parameters are optional in the schema, but the description says 'compare two versions' without explaining what happens when only service is provided or how defaults are resolved.

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?

All three parameters are already fully described in the schema with 100% coverage, so the baseline applies. The description's 'compare two versions' phrasing aligns with fromVersion and toVersion but does not add extra semantic detail 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 what the tool does: compare two versions of a third-party API and return breaking changes, with specific examples of the output (removed endpoints, parameter type changes, removed request body fields, migration guides). It also distinguishes itself from the sibling tool factreason_package_upgrade_advisory by explicitly naming the alternative context.

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 provides an explicit routing rule: use factreason_package_upgrade_advisory for npm or PyPI packages, implying this tool is for other third-party APIs. This gives the agent clear guidance on when to select this tool versus the named alternative.

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