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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds value beyond annotations by disclosing that each request costs money and that no API key is required. However, it does not address failure modes, whether invalid emails still incur charges, rate limits, or what the open-world hint implies about result completeness.

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?

Two sentences with zero filler: the core function is front-loaded in the first sentence, and the second packs the cost and auth model compactly. Every clause earns its place.

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?

For a single-parameter tool with an output schema and read-only annotations, the description adequately covers function, cost, and auth requirements. The main gap is that among 37 siblings — including the near-identical email_enrichment — there is no explicit statement distinguishing when the MPP variant should be selected over the standard one; the agent must infer it from the payment model.

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% — the schema already documents the email parameter with format, pattern, and a description ('The email address to enrich'). The tool description restates the enrichment concept but adds no new syntax, validation, or formatting semantics beyond what the schema provides, so the baseline 3 applies.

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 uses a specific verb ('enrich') with a clear resource (an email address) and states the expected output (detailed contact and company information). The MPP mention separates it from the non-prefixed sibling email_enrichment, but it does not explicitly contrast with mpp_email_finder or mpp_email_verifier — though their verbs do convey different jobs.

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 pay-per-request and no-API-key facts are a genuine usage signal: they tell an agent this MPP variant is the metered alternative to sibling tools that require a key or subscription. However, no alternative is named and no when-to-use vs when-not-to-use guidance is given, so the selection logic is left mostly to inference.

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