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

With no annotations, the description fully explains the behavioral traits: it explicitly discloses that `breaking:true` is a compatibility claim, not importance; `mustAct` should be checked first and may indicate the integration is already failing; and `entries[].action` should be read. This is excellent transparency for a read-only changelog tool.

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 three sentences, each earning its place: it opens with the tool's purpose, then explains usage, and ends with critical interpretation guidance. It is appropriately sized and front-loaded, though it could be slightly condensed without losing 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?

Given only one parameter and no output schema, the description adequately covers the return fields (`breaking`, `mustAct`, `entries[].action`) and the interpretation workflow. It doesn't address error handling or invalid versions, but for a simple changelog tool it is sufficiently complete.

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 schema already provides 100% coverage for `since` with 'the API version you built against.' The description adds a similar phrase and clarifies the filter behavior, but it doesn't introduce new information beyond the schema, so the baseline 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 clearly states the tool provides 'Machine-readable API history' and returns what has changed since a given version, with a specific verb and resource. It distinguishes itself from siblings by focusing on versioned changes and compatibility impact, which no other sibling tool name suggests.

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 clear usage context by instructing to pass the build version as `since` and explains the workflow of checking `mustAct` first and reading `entries[].action`. It doesn't explicitly name alternatives or exclusions, but the context is unambiguous, so no further guidance is needed.

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