Version Diff (free, keyless)

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

Beyond the annotations (read-only, open-world, idempotent), the description discloses important behavioral traits: rate limits (25 calls/day per client IP), quota reset time, behavior when over quota (redirects to paid route), error behavior for unresolvable versions (422 error, never partial diff), and the signed attestation output. This adds significant context beyond what annotations provide.

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 uses clear section labels (WHAT, WHEN, WHEN NOT, COST, OUTPUT) to front-load the core purpose and provide scannable details. Every sentence contributes value—purpose, usage guidance, error behavior, pricing, and output structure—with no filler or redundancy.

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 complexity (4 required parameters, output schema, rate limits, paid routes, signed attestation), the description is remarkably complete. It covers the operation, usage context, failure modes, cost structure, and output keys, leaving little ambiguity for an agent deciding whether and how to invoke it.

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?

The input schema already documents all four parameters with clear descriptions (ecosystem, package, from_version, to_version) at 100% coverage. The description does not add additional parameter-level meaning beyond what the schema provides, so the baseline score of 3 is appropriate.

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 precise action: "symbol-level diff between two pinned versions of one package" and enumerates the specific outputs (added, removed, changed signatures, new deprecations, breaking/additive/neutral classification). This clearly distinguishes it from sibling tools like attester_package_exists or attester_symbol_signature, which serve different purposes.

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 gives an explicit use case ("before upgrading a dependency, or when reviewing what an upgrade breaks") and a 'WHEN NOT' statement about unresolvable versions. However, it does not name alternative tools for cases where a diff cannot be performed, so it lacks the explicit alternative guidance that would earn a 5.

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