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

Annotations already declare read-only, idempotent, non-destructive behavior, but the description adds important operational context: billing per returned row, that limit caps both rows and cost, follower-count ordering, case-insensitive substring matching, and that results are user-generated untrusted content. This goes well beyond the structured 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 dense but front-loaded, starting with the core purpose before routing guidance, return fields, and billing/trust notes. Every sentence earns its place by adding selection, parameter, or safety context.

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 compensates by listing the returned short-row fields explicitly. Annotations cover safety, the parameters are fully documented, and billing and untrusted-content caveats are included, so an agent has everything needed to invoke correctly.

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%, so the baseline is 3, but the description adds meaningful semantics: query is a partial username/full name with case-insensitive substring matching, and limit caps both returned rows and cost. It does not add format or syntax details beyond that, but the added cost and matching behavior is valuable.

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 states a specific verb and resource ('Search Instagram accounts') plus matching semantics and ordering. It explicitly distinguishes this tool from siblings by naming get_user_by_username for exact handles and get_top_users/search_users_by_demographics for other filtering needs.

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?

It states exactly when to use this tool ('when you only know part of a name') and names three alternative sibling tools with the conditions that select them. This leaves little to inference.

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