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

Annotations already declare readOnlyHint=true, so the safety profile is covered structurally, and the description correctly stays consistent with that. It adds the returned fields (contacts, address) and the backing route, but says nothing about pagination defaults, result caps, or ordering behavior beyond what the schema documents.

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 with the purpose front-loaded and zero filler. The trailing 'Invoice Ninja: GET /api/v1/vendors' is a route mapping that adds little to tool selection, a minor but real dilution.

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 saying what comes back, and it does so at a high level ('with contacts and address'). Pagination and per-page defaults live in the schema, so the remaining gap is mainly how results are ordered or shaped at the envelope level.

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 all six parameters (page, per_page, sort, filter, number, status) carry their own descriptions, so the baseline of 3 applies. The description adds no syntax, default, or interaction detail beyond the schema, so it does not lift the score.

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 (list vendors) and immediately disambiguates the term with the synonym '(suppliers)', which matters because siblings are dominated by client/invoice/expense list tools. It also declares the payload shape ('with contacts and address'), so an agent knows what it gets without opening a 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 rather than stated: there is no explicit when-to-use, when-not, or alternative named, but there is no sibling 'get_vendor' that competes with it, so the selection decision is unambiguous by default. It never tells the agent how this relates to filtering (e.g. use 'number' for a single vendor vs 'filter' for broad search), leaving that to the schema.

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