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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds the fact that it fetches public information and that post IDs are shortcodes, but does not disclose edge cases (e.g., private profiles, rate limits) or behavioral traits beyond what annotations provide. It adds minimal value beyond the annotations.

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?

The description is two concise sentences with no redundant wording. The primary purpose is front-loaded, and the cross-reference to instagram_post is a useful addition without bloat.

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 read-only tool with one parameter and no output schema, the description is largely complete: it lists returned fields and explains the shortcode relationship. It could mention that the profile must be public, but that is implied by 'public profile information' and the annotations. Minor gaps like error handling are not critical for this simplicity.

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 username parameter is fully documented in the schema. The description does not add any additional semantic meaning about the parameter beyond what the schema provides, maintaining the baseline of 3.

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 explicitly states the tool fetches public profile information from Instagram, lists the returned fields (bio, counts, posts, etc.), and clearly distinguishes the resource from the sibling tiktok_profile by naming the platform. It is a specific verb+resource with no ambiguity.

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 gives clear guidance on how to use the returned post IDs (pass to instagram_post) but does not explicitly state when to choose this tool over alternatives like tiktok_profile. It implies usage for Instagram profile data but lacks explicit exclusions or when-not-to-use conditions.

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