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

No annotations are provided, so the description carries the full burden. It does disclose the return shape in detail, including the bounce object and its enum-like values, which is genuinely useful. However it omits key behaviors such as what happens when the email is not found, error conditions, or auth requirements.

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 purpose is front-loaded in the opening clause, and the remaining text is devoted to output detail that earns its place. The single dense sentence is somewhat heavy but not padded.

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 description compensates by describing return fields and the bounce structure, which is the key complexity. For a one-parameter lookup this is largely complete, though not-found behavior is left unstated.

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?

There is a single required parameter and schema coverage is 100%, so the schema already fully documents 'email'. The description reinforces that the lookup is by correo but adds no syntax or format detail beyond the schema; 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?

States a specific verb and resource: it finds a contact by email and returns its data, status, tags, and basic history. This is clearly a read-by-email lookup, implicitly distinct from create_subscriber/update_subscriber siblings. It does not, however, explicitly name an alternative tool to contrast with.

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?

Usage is implied — search a subscriber by email — but there is no explicit when-to-use, when-not-to-use, or reference to an alternative such as list_lists or get_campaign_audience. The agent can infer the context but is given no routing guidance.

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