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

Annotations declare readOnlyHint=false, so this is state-changing, yet the description frames it as a passive 'check' and never mentions the write, the cost/costMicros accounting, or the idempotencyKey requirement. Annotations do cover the safety profile (destructiveHint=false, openWorldHint=true), but the description still hides the mutation and billing side effects that matter for invocation.

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?

A single front-loaded sentence with no filler, which is structurally clean. But brevity here is under-specification rather than economy: eight required parameters and a mutation are dispatched with nine words.

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?

No output schema exists, so the description would need to explain the return, and it does not; it also omits the recording behavior implied by required status/source/provider/costMicros fields. With 10 parameters, 0% schema coverage, and no annotations detail added, an agent lacks what it needs to call this correctly.

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 0% across 10 parameters (8 required), and the description adds no parameter meaning at all — nothing about status values, provider/source semantics, costMicros units, or the idempotency key. For a tool this parameter-heavy, the description fully fails to compensate for the undocumented schema.

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?

Names a verb (check/verify) and a resource (a contact's email deliverability), so the basic intent is legible. However, it never clarifies whether the tool performs the deliverability check itself or records a caller-supplied result, and it does nothing to distinguish itself from sibling verification tools such as verify_article_publication or check_backlink. The purpose is stated but left ambiguous at the exact point that matters.

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?

There is no guidance on when to call this tool versus alternatives (e.g., list_contacts, suppress_contact, find_prospect_contact) and no mention of prerequisites. The agent must infer placement in the workflow entirely from the name.

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