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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), so the description earns credit for going further: it discloses the data-coverage limitation (posts_analyzed can be lower than the real post count) and a trust warning about user-generated content. These are non-obvious behavioral traits an agent could not infer from structured fields.

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 tight sentences: capability + returns first, then routing guidance, then caveats. Every sentence carries distinct information (scope, alternative, coverage limit, trust note) with no filler.

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, listing the returned fields is genuinely necessary and it does so. Combined with the coverage caveat and trust warning, an agent has everything needed to call and correctly interpret this tool.

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?

There is a single parameter with 100% schema description coverage ('Instagram user ID (pk)'), so the schema already does the work. The description adds no syntax, format, or identification nuance beyond what's there, making the baseline 3 appropriate.

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?

Opens with a specific verb+resource ('Calculate engagement metrics for one Instagram account') and enumerates the concrete outputs (posts_analyzed, average/total/max likes and comments, engagement_rate, username, follower_count, country, registration_date). This clearly distinguishes it from sibling analysis tools like get_top_users or get_stats.

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?

Gives an explicit use case ('judge an account's audience quality') and names the alternative for the adjacent need ('use get_user_medias to see the underlying posts'). It also flags the boundary condition that only DB-collected posts are counted, which steers correct interpretation rather than misattribution.

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