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

Annotations already declare readOnly, idempotent, and non-destructive hints. The description adds valuable behavioral details: the response structure, the null/empty email behavior as a normal result (not an error), the single-creator-per-call limit, and performance metrics (533 bytes, ~2 seconds). No contradiction with 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 thorough but organized: main purpose first, then return fields, edge case, performance, and finally usage guidance. Each sentence earns its place, though it could be trimmed slightly without losing value. It is front-loaded with the core purpose.

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?

Given an output schema exists and only one parameter is present, the description covers everything needed: return shape, edge cases, performance expectations, and how it relates to a sibling tool. Nothing an agent needs to correctly invoke this tool 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 the parameter 'url' is already well-described as a TikTok/Instagram/YouTube profile URL. The description reinforces this and adds the constraint that it handles one creator per call, which clarifies the parameter's scope. This slightly exceeds the baseline.

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 opens with a specific verb ('Looks up') and resource ('contact emails for one TikTok, Instagram or YouTube creator from a profile URL'), and lists the full set of returned fields. It also distinguishes itself from the sibling post_waveinflu_similar_creators by stating that this endpoint handles Instagram creators and fills email gaps.

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 explicit guidance: use post_waveinflu_similar_creators first to build a list, then call this endpoint for creators with null emails and for Instagram creators. It clearly states when not to use this tool, leaving no ambiguity.

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