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

Annotations already declare readOnlyHint=true and idempotentHint=true, covering the safety profile. The description adds useful behavioral context by specifying the return fields and that it lists registry entries, with optional filters. It doesn't describe edge cases like empty results or pagination, but for a simple list tool with read-only annotations, the added context is sufficient.

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 concise sentences: the first states the action and filters, the second explains the output and the use case. Front-loaded with the core purpose and free of filler. 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?

Given the tool's simplicity, the presence of an output schema (which covers return format), and comprehensive annotations, the description is complete. It explains what the tool does, why to use it, and what information it returns. No critical information is missing for an agent to invoke it correctly.

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?

The input schema provides 100% coverage: both parameters (query and category) have detailed descriptions with examples and the enum list is fully spelled out. The description adds no additional parameter semantics beyond what the schema already documents, so a baseline 3 is appropriate.

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 states a specific verb ('List') and resource ('vendors in the built-in registry') and immediately clarifies the optional filters and the output fields (slug, display name, category, status page URL). It is readily distinguishable from sibling tools, which all target other domains (certs, DNS, incidents, status, stacks).

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?

Explicitly states when to use the tool: 'Use to discover the correct slug to pass to other tools, or to see which vendors are available before configuring a stack.' This provides clear context and a concrete purpose, effectively guiding the agent on appropriate invocation without ambiguity.

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