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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds useful content-shape context (what fields come back) and a provenance warning about API Evangelist publishing keys, but says nothing about pagination, the `next` affordance semantics, or result limits.

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?

Two front-loaded sentences; the first delivers the payload contents and the second delivers the one non-obvious caveat. No filler, though the provenance warning is tangential to the tool's invocation and could be tighter.

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?

With no output schema present, the description carries the burden of describing return content and does so field-by-field. For a read-only single-record lookup with fully documented parameters, this is nearly sufficient; minor gaps remain around the `next` block and result sizing.

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%: slug format/example, view enum, context semantics, and include_next are all documented in the schema itself. The description adds no parameter-level meaning beyond that, 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 specific verb/resource combination (fetch one OpenAPI specification extension) and enumerates the payload fields — publishers, occurrence and document counts, appearance locations, value shapes — so an agent knows exactly what it returns. It implicitly routes from the sibling find_extensions by noting the slug format, but never states the detail-vs-list distinction explicitly.

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?

Usage is implied rather than stated: the slug is 'as find_extensions returns it', which hints this is the follow-up detail call. The 'CHECK is_api_evangelist BEFORE treating a key as provider-originated' line is a data-interpretation caveat, not tool-selection guidance, and no when-not-to-use condition is given.

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