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

The readOnlyHint=true annotation already carries the safety profile, so the description's burden is reduced. It adds the returned field set and the API mapping, but says nothing about behavior beyond the happy path — no 404/not-found handling, permission requirements, or response envelope shape.

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?

A single, front-loaded sentence giving the action, identifier, and returned payload, followed by the endpoint mapping. No redundancy or 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?

With no output schema, the description usefully compensates by enumerating the fields returned. Combined with the readOnly annotation and fully documented single parameter, an agent has what it needs to invoke the tool correctly; only error behavior is unaddressed.

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?

There is only one parameter and schema description coverage is 100% ('The lead id.'), so the schema already documents it fully. The description's 'by id' adds nothing beyond the schema, which is the expected baseline of 3 when the schema does the heavy lifting.

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 pairs a specific verb and resource ('Fetch a single lead by id') and enumerates what that lead contains (customer, address, source, tags, assigned employee, status, pipeline status), plus maps to the underlying endpoint. The phrase 'single ... by id' functionally distinguishes it from the sibling list_leads without the agent needing to open either 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?

Usage is implied: you need a lead id to call it, so this is the lookup tool when the id is known. However, the description never states when to prefer this over housecall_list_leads, nor any exclusions or failure conditions (e.g. unknown id). Guidance is present only by inference.

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