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

Annotations cover the safety profile (readOnlyHint, openWorldHint), so the description's job is to add context — and it does: 'top comments' signals that results are a subset, the returned fields are enumerated, and the explicit 'Cost: 3 credits' is a genuinely useful operational disclosure. Pagination behavior is not stated, keeping it short of a 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?

Two short sentences plus a cost line, all front-loaded with the core purpose first. No filler, though the return-field enumeration and cost line could be merged more tightly.

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, the description usefully describes what comes back (fields plus total comment count), and it discloses cost. Missing only pagination/limit behavior for a comments endpoint, which likely returns capped results.

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 parameters (url, shortcode) are already documented in the schema, including the either/or relationship. The description adds no format or usage detail beyond that, so 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?

States a specific verb and resource: 'Get comments on an Instagram post,' and enumerates the returned fields (author, text, time, likes, reply count). It is clearly distinguishable from instagram_comment_replies in practice, but does not name that sibling explicitly to differentiate scope.

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?

No when-to-use guidance, no mention of when to prefer instagram_comment_replies for threaded replies, and no prerequisites. The only implied usage signal is the 'top comments' phrasing, which hints at a partial result.

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