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

Annotations already declare the safety profile (readOnlyHint=false, openWorldHint=true, non-idempotent, non-destructive). The description adds genuinely useful cost disclosure (email 1 credit, demo fixtures free), but leaves unclear why the tool is non-read-only, whether credits are charged on error, and what 'signals' are returned beyond a vague mention.

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?

Three short, front-loaded sentences: purpose first, then return shape, then cost. The cost sentence, however, introduces phone and IP credits that are irrelevant to this tool and briefly confuse the reader.

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?

There is no output schema, zero parameter documentation, and the description does not compensate: 'returns signals and a summary' does not tell the agent what signal types or risk levels to expect, and the two optional parameters are entirely unexplained. For a credit-consuming, non-read-only check, this leaves real gaps.

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% for all three parameters. The description only implies the 'email' input and says nothing about 'country' or 'idempotency_key', so an agent cannot tell whether country affects results or when to reuse an idempotency key. The credit sentence mentioning 'phone 1, IP 1' adds noise rather than parameter meaning.

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?

States a specific verb and resource ('Check email') plus the use case ('signup or lead-list quality'), which is enough to separate it from check_ip and check_phone. Differentiation from the closest sibling (check_signup) is only implicit, since both mention signup quality.

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?

No explicit when-to-use guidance and no routing to alternatives, even though check_signup overlaps directly with the stated 'signup quality' purpose. The agent must infer from the tool name alone which of the four checks to call.

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