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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), and the description adds substantial behavior beyond them: snapshots hold content hashes not bodies so schemas are not diffed, `detail` returns the release-asset location for both months, and a month without a snapshot errors with the valid months rather than returning a misleading empty diff. This is exactly the kind of edge-case disclosure the annotations cannot carry.

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 behavior, then layered usage, limitation, and error handling, each paragraph earning its place. The prose is slightly narrative ('still the same server that code was written against') but nothing is redundant.

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?

There is no output schema, so the description carries the return burden and does so: 'The answer names the changed tools and the kind of change,' plus the fallback path for exact diffs and the error-on-missing-month contract. Nothing an agent needs to invoke this correctly is missing.

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 both `name` and `since` are fully documented in the schema, including the namespaced format and the omitted-`since` default. The description reinforces the month-vs-latest framing but adds no syntax or format detail beyond the schema, so the baseline of 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: it reports which tools were added, removed, or had descriptions/schemas changed between a named month and the latest snapshot. It also explicitly separates itself from its sibling ('A liveness check says a server answers today; this says whether it is still the same server that code was written against'), so an agent can route between mcp_liveness_check and this tool without opening a schema.

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?

Provides concrete when-to-use triggers (a server that behaved differently, a prompt/integration that started failing, before trusting a cached description) and contrasts the tool's purpose against the liveness check. The guidance is actionable and leaves nothing to inference.

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