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

Annotations already declare destructiveHint=false and openWorldHint=true; the description goes further by disclosing that nothing is sent to anyone, that the record can be edited afterwards, and that a Cotlet API key with app access is required. It does not cover rate limits or idempotency, so it falls short of a 5.

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 the core action and its guardrail, but the first two sentences restate the same idea ('Add a customer...' / 'Adds one customer...'), which is mild redundancy rather than a structural flaw.

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, yet the description notes the return value is the customer number, and the mutation's safety/permission profile is covered. The remaining gap — nothing about failure modes or duplicate handling on rejection — is minor.

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 coverage is 100%, so the schema already documents all four parameters, including the delivery_method enum. The description names three of the four fields but adds no syntax, format, or default information beyond what the schema provides — the expected baseline of 3.

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+resource ('Add a customer to the customer register') plus the key fields supplied. It also implicitly distinguishes itself from the sibling list_customers by telling the agent to run that first, so an agent can differentiate it without opening schemas.

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?

Gives an explicit precondition ('Run list_customers first so you do not create a duplicate') and a clear autonomy rule ('runs without asking first'), which is exactly the when/how guidance an agent needs before invoking a write tool.

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