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

readOnlyHint=true already declares this is a safe read, so the description's only behavioral claim ('GET /invoices') is redundant with the annotation. It adds nothing about pagination defaults, ordering behavior, or result shape, leaving no value beyond structured data.

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 short sentences, front-loaded with the primary action and filter. The trailing 'GET /invoices' is redundant HTTP detail but does not bloat the definition meaningfully.

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?

A simple read-only list tool whose five parameters are fully documented in the schema and whose safety profile is covered by annotations; no output schema exists so return values need not be described. It is nearly complete, only lacking explicit sibling routing.

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 the schema already documents page, per_page, sort, order, and patient_id with formats and defaults. The description's mention of the patient filter merely repeats schema content, so baseline 3 applies.

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 (list) and resource (invoices) plus the optional patient filter, which is enough to tell it apart from cliniko_get_invoice. It does not explicitly name a sibling or scope boundary (e.g., all invoices across the account), so it stops short of 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?

The phrase 'optionally filtered by patient' implies the use case of narrowing by patient, but there is no explicit when-to-use/when-not guidance or routing to alternatives like cliniko_get_invoice for a single record. Usage is only implied.

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