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

With no annotations, the description carries the full burden and does well: it discloses per-page pricing (1 credit/page), the required Authorization: Bearer api_key, pagination behavior, and that play metrics are only included 'when available'. It omits rate limits and error/edge behavior, keeping it short of 5.

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-loads the core purpose, but the trailing metadata is repetitive ('Priced per page... Costs 1 credit(s)... Credits unit: page') and includes a stray double period. Some sentences do not earn their place.

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?

For a fetch tool with no output schema and no annotations, the description covers the key facts an agent needs: what is returned (captions, play metrics), pagination, cost, and auth. It is nearly complete, missing only rate/error details.

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 the baseline is 3. The description only restates the depth default ('defaults to 1 page') already documented in the schema and adds no syntax or format meaning beyond it.

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?

Names a specific verb (Fetch) and resource (recent reels) with scope (for a user id), which distinguishes it from instagram_posts and instagram_post siblings. It does not explicitly contrast itself with those siblings, so it stops short of a 5.

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 never states when to use this tool versus alternatives, nor any prerequisites or exclusions. Only implicit context (reels-of-a-user) hints at usage; no routing guidance for the many sibling tools is provided.

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