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

readOnlyHint=true already establishes the safety profile, so the bar is lower. The description adds genuinely useful behavioral context beyond annotations: the response includes the customer's addresses and their ids are the input to downstream job/estimate creation, which is the key thing an agent must know before calling.

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?

Two compact clauses, front-loaded with the action and payload, plus a short API endpoint mapping. Every sentence earns its place with no filler.

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 two-parameter read with full schema coverage and no output schema, the description covers purpose, payload, and downstream use. Minor gaps remain around the expand parameter and not-found behavior, which keeps it from a 5.

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 both customer_id and expand are already documented in the schema, and the description adds only that the id lookup is the entry point. Baseline 3 is appropriate; the description adds no format or syntax detail beyond the schema.

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 ('Fetch a single customer by id') and implicitly separates itself from housecall_list_customers via 'single'. It also names the returned payload (addresses), but never names an alternative sibling explicitly, so it stops short of a 5.

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 reason to call it: the address ids returned are needed 'to create a job or estimate', which effectively tells the agent when this tool belongs in a workflow. There is no explicit when-not or named alternative (e.g. versus list_customers), so it is not a 5.

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