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

Annotations already mark readOnlyHint=true, and the description reinforces this by stating 'GET /virtual-keys/{slug}', making the HTTP method and read-only nature explicit. It adds useful behavioral context by noting the response includes provider and limits, though it does not cover error/edge-case behavior.

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 are front-loaded with the core behavior before the endpoint reference. Every phrase earns its place, with no verbose repetition of the title or schema.

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 one-parameter read-only lookup, the description provides the resource, the lookup identifier, and the main response content (provider + limits). With annotations covering safety and no output schema required, it is reasonably complete, though exact error behavior is left unspecified.

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 schema already fully documents the only parameter, slug, at 100% coverage. The description repeats the slug lookup concept without adding format, constraints, or usage detail beyond the schema, so the baseline score of 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?

The description opens with a specific verb ('Get'), a precise resource ('single virtual key'), and the lookup key ('by slug'), and names the response highlights ('provider + limits'). 'Single' clearly distinguishes it from the sibling list_virtual_keys tool.

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 phrasing 'a single virtual key by slug' establishes the context for fetching one specific key, implicitly contrasting with list_virtual_keys for multiple keys. It does not explicitly name alternatives or exclusions, so it stops short of the strongest guidance.

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