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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered. The description adds genuine behavioral context beyond that: the scope of returned data (jobs, estimates, invoices) and the authorization requirement (a Cotlet API key with access to the app).

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 sentence and the second sentence restate the same return contents ('One customer with contact details, notes, upcoming jobs, open estimates and invoices' vs 'Returns one customer with contact details and property notes, plus their upcoming jobs, open estimates and unpaid invoices'), which is redundant. The usage and auth sentences do earn their place.

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 carries the burden of describing the return payload, which it does in detail, and it adds the auth prerequisite. Complete enough for a single-parameter read tool in this context.

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?

The single parameter has 100% schema description coverage ('Customer ID from list_customers'), so the schema already carries the semantics. The description adds nothing about the ID format or where it is obtained beyond what the schema says; 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+resource ('One customer') and enumerates exactly what is returned: contact details, property notes, upcoming jobs, open estimates, unpaid invoices. This clearly separates it from the sibling yardbook_list_customers, which returns many customers.

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 a concrete usage context: 'Use it before scheduling or billing so your agent sees what is already there.' It does not explicitly name list_customers as the alternative for enumerating customers, so it stops short of full when/when-not routing, but the intended context is clear.

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