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

With annotations already covering the safety profile (readOnlyHint=false, destructiveHint=false, openWorldHint=true), the description adds meaningful context: it does not notify anyone ('reaches no one'), only mutates the customer list, so it 'runs without asking for your OK', and it states the Cotlet API key requirement. This is useful non-obvious behavior beyond the annotations.

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 first two sentences are largely redundant — the second restates the first almost verbatim ('Adds a customer... with the service address and contact details'). Front-loaded purpose is good, but the duplication costs it a point.

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?

For a create tool with no output schema, the description covers the action, auth requirement, and behavioral safety profile. It stops short of describing the return value (e.g. the new customer ID) or duplicate-handling behavior, but is otherwise complete against the rich annotations.

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 six parameters and the type enum. The description only restates 'contact details and service address' and the prospect type, adding little syntax or meaning beyond the schema. 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?

The description states a specific verb and resource ('Add a customer or prospect with contact details and service address'), making the action unmistakable. It distinguishes the customer/prospect duality via the type parameter, but does not explicitly name sibling tools like yardbook_get_customer or yardbook_list_customers to differentiate scope.

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 ('Add a customer, or a prospect if type is prospect'), which tells the agent there are two creation modes. However, there is no explicit when-to-use versus when-to-use-an-alternative guidance, no prerequisites beyond the API key, and no note on what to do if the customer already exists.

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