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

Goes well beyond the annotations: it specifies the return values (contact_id and, for a customer, the customer number), clarifies that the call 'sends nothing to anyone, books nothing,' that the contact is editable afterward, and that a scoped Cotlet API key is required. This is rich side-effect and auth context that the readOnlyHint/destructiveHint flags alone do not convey.

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?

Front-loaded with purpose, then return values, precondition, side-effect profile, and auth requirement. Each sentence carries distinct information, though the density is near the limit for a single-verb tool.

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 fills that gap by describing what is returned. Combined with the dedup precondition, the no-side-effects disclosure, and the auth requirement, an agent has everything needed to invoke it 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 100%, so the schema already documents all five parameters (name, role, email, phone_number, organisation_number). The description mentions some fields but adds no syntax, format, or constraint detail beyond what the schema provides. Baseline 3 is appropriate.

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 ('Add a customer or supplier'), names the distinguishing fields, and separates itself from the read-only sibling list_contacts. An agent can identify the operation without opening the schema.

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?

Explicitly routes the agent: 'Run list_contacts first so you do not create a duplicate.' This gives a clear precondition and alternative. It lacks an explicit when-not-to-use statement, but the dedup guidance is actionable.

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