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

Beyond the readOnlyHint annotation, the description discloses real behavioral costs: 'Costs 1 Sliq credit per verified hit. Free when the user has connected their own Apollo key.' It also explains the 429 throttle behavior and distinguishes transient rate-limiting from a permanent no-match result. This meaningfully exceeds what the annotation alone conveys.

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 core purpose is front-loaded in the first sentence, with use cases, alternatives, cost, and return behavior following in a logical order. The phrasing is mostly efficient, though the 'queue boundary' explanation in the setup_email_sequence suggestion is somewhat jargon-heavy and could be clearer.

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 <returns> section does its job by defining success shape, no-match shape, and the rate-limited shape. The description covers inputs, provider, cost, alternatives, and error semantics, making it complete for an agent to decide when to call it and what to expect.

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 description coverage is 100%, so the schema already documents both parameters: email and optional name for narrowing the match. The description restates email as the lookup key but adds no new parameter-level meaning beyond the schema, matching the baseline expectation.

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: 'Find a LinkedIn profile URL for a person given their email, using Apollo.io.' It also identifies itself as 'The reverse of find_email', which clearly distinguishes it from a key sibling tool without requiring schema inspection.

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 concrete usage contexts: deduping a later LinkedIn step against an email step, and supplying the URL required by find_phone_number. It also explicitly names an alternative, setup_email_sequence(enrich=True), and says to prefer it for email outreach when LinkedIn touches may follow. This is strong, actionable routing guidance.

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