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

Annotations already cover the safety profile (readOnlyHint, openWorldHint), yet the description adds substantial context beyond them: the 25-result cap, the fact that work emails are deliberately omitted, and an explicit billing model ('3 credits per result... 75 for a full page') including the 'no results, no charge' guarantee. That cost and chaining information is exactly the kind of behavior structured fields cannot convey.

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?

It is front-loaded with the core capability and return shape, then layers usage, exclusions, chaining, and cost in short declarative sentences. Every sentence carries actionable information with no padding or repetition.

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?

Despite having no output schema, the description enumerates the returned fields (name, title, company, profile link), the result ceiling, the cost model, and the downstream call needed for emails. For a five-parameter search tool this covers everything an agent needs to invoke it correctly and budget the call.

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?

With 60% schema coverage the description usefully reinforces filter semantics (country as ISO-2, count as a spend cap of 1-25) and adds a constraint absent from the schema: at least one filter must be supplied despite zero required parameters. The 'location' parameter is left unelaborated, so it stops just short of full coverage.

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 and resource ('Finds people') plus the exact filter dimensions and the four returned fields, so the agent knows precisely what it gets. It explicitly distinguishes itself from siblings, naming apione_email_find and apione_people_enrich with the conditions that select them.

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 the intended use ('identify who to contact at a company'), the excluded use ('Not for details on one named person'), and routes to the correct alternatives for emails and enrichment. It also gives operational guidance ('Give at least one filter', 'Set count to cap spend'), leaving nothing to inference.

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