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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds meaningful context beyond that ('public posts by other accounts,' credit cost), but says nothing about pagination behavior or what the returned payload contains. Compared to the calibration baseline for an annotation-covered read tool, this is a solid but modest addition.

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?

Three short sentences, front-loaded with the core action and data semantics, then use cases, then cost. No filler, though the second sentence slightly overlaps the first.

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 simple, credit-costed read tool with 100% schema coverage, annotations, and no output schema, the description covers scope, purpose and cost adequately. Pagination is only implied by the cursor parameter, which is a minor omission.

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% – cursor, user_id and username are each documented in-schema, including the 'pass this or the other' relationship. The description adds no parameter-level meaning, 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?

States a specific verb and resource ('Get posts an account is tagged in') and sharpens it with 'Public posts by other accounts that tag this account,' which separates it from the account's own post feeds. It does not name the sibling it contrasts with (e.g. instagram_posts/media), so differentiation is inferential rather than explicit.

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 use cases ('UGC, brand mentions and influencer tracking') imply when the tool is relevant, giving implied usage. There is no when-not guidance, no explicit alternative for retrieving an account's own posts, and no note that either user_id or username is required (that detail lives only in the schema).

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