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

Annotations cover readOnly and openWorld, and the description adds the 'public account' access constraint plus a credit cost, which is genuinely useful behavioral context. However it omits failure behavior for private/suspended accounts and doesn't mention rate limits beyond the flat cost.

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: purpose first, payload second, cost last. No filler, no repetition of the title, and front-loaded with the key information.

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 read-only profile lookup with no output schema and full schema coverage, the description gives enough: what it returns, the account-type constraint, and the cost. Only the omission of private-account failure semantics and sibling routing keeps it from a 5.

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 coverage is 100% and the schema already explains that user_id and username are alternatives ('Pass this or user_id') and that handles/URLs work. The description adds nothing beyond the schema, 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+resource ('Get an Instagram profile') and enumerates the exact data returned (follower/following/post counts, bio, links, category, verification, profile picture), which distinguishes it from siblings like instagram_username or instagram_user_id (resolution) and instagram_followers (list).

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 implies usage by scoping to 'any public account' and clarifying the return payload, but it never explicitly says when to use this versus instagram_username/instagram_user_id (ID resolution) or instagram_insights (metrics). With 27 siblings, an explicit alternative would have been valuable.

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