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

Annotations already cover readOnly/idempotent/non-destructive, but the description adds substantive context they don't: results are ordered by follower count, billing is per returned row, limit caps both rows and cost, and the content is user-generated and should be treated as untrusted. This is well beyond the annotation baseline.

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?

Front-loads purpose and the illustrative example, then alternatives, then return/billing/trust notes. Every sentence carries distinct information with no redundancy or 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 present, the description still specifies the return shape ('up to limit short profile rows, same fields as search_users') and the safety caveat. No output schema means no burden to explain further; nothing an agent needs is missing.

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 baseline is 3, but the description adds genuine meaning: location is a substring match rather than exact, and limit controls both row count and billing cost. These non-obvious semantics go beyond the schema's terse 'Location or city name' and 'Max rows to return' texts.

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 ('Find Instagram accounts that posted from places whose name contains the query') and clarifies the matching semantics with a concrete example ('Paris'). It explicitly distinguishes itself from search_users_by_demographics and search_locations, so an agent can route correctly without opening schemas.

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?

Explicit when-to-use ('audiences by posting place') plus two named alternatives with the conditions that select them: search_users_by_demographics with city/country for profile-stated location, and search_locations to inspect places first. Nothing is left to inference.

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