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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds the GET method and id-based lookup, but does not disclose behavior such as error handling, response format, or authentication requirements. It adds modest context beyond 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 description is two short clauses with no filler. It is front-loaded with the action and resource, then gives the endpoint. Every word earns its 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?

For a simple get-by-id tool with one parameter and a read-only annotation, the description is mostly complete. The only minor gap is that without an output schema, it does not explicitly state what the returned invoice data will look like, but this is reasonably inferable from the resource name.

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%, and the description's '{id}' reference directly mirrors the documented 'id' parameter. The description adds no additional meaning beyond the schema already provides.

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?

Description uses a specific verb ('Fetch') and resource ('a single invoice by id'), and includes the exact HTTP endpoint. This clearly differentiates it from sibling list tools like cliniko_list_invoices and other get_* tools.

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?

The description implies usage for retrieving one invoice by ID, but it does not explicitly state when to use this tool versus cliniko_list_invoices or other get_* tools. No exclusions or alternative routing are provided.

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