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

Annotations already indicate readOnlyHint=false, idempotentHint=false, and destructiveHint=false. The description adds no extra behavioral context: it does not explain duplicate handling, error behavior, whether an API key is required despite appearing in the schema, or what happens if the list_id is invalid.

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 description is very short and front-loaded with a clear purpose. The second sentence about required fields is redundant with the schema, so not every sentence earns its place, but the overall structure is efficient and free of unnecessary detail.

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?

This tool has 14 parameters, nested objects, and no output schema, yet the description only states the basic operation. Missing context includes return value, duplicate/error handling, how API key authentication works, and the relationship to sibling batch/upsert tools, making the description inadequate for correct invocation in many scenarios.

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 baseline is 3. The description repeats that email and list_id are required, which the schema already conveys, and does not add any additional meaning about parameter formats, constraints, or relationships.

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 clearly states the verb 'create' and the resource 'a contact in a MailerCloud list', immediately conveying the core function. It does not explicitly differentiate from sibling tools like batch_create_contacts or upsert_contact, but the basic purpose is unambiguous.

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 guidance is given on when to use create_contact over batch_create_contacts, upsert_contact, or update_contact. It also omits prerequisites such as list existence or authentication requirements, leaving the agent to infer usage solely from the tool name.

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