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

Annotations already declare readOnlyHint=true, so the trailing 'Read-only' adds nothing, but the description goes further by disclosing the return content: the validation verdict, the RFC1035-normalised form, and any conflicting existing credential. With no output schema present, this genuinely informs the agent about what it will get back.

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 sentences, zero waste, with the core purpose front-loaded and the return behavior following. The 'Read-only' tag is somewhat redundant with the annotation but costs almost nothing.

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 single-parameter validation tool with no output schema, the description covers purpose, the organisation-scoped availability check, the read-only nature, and precisely what the response contains. Nothing an agent needs in order to call it correctly is missing.

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 (100% coverage) already documents the single parameter as 'The candidate credential name'. The description adds meaning beyond that by indicating the name is validated and RFC1035-normalised, which tells the agent what form of input is expected. Slight value-add over the baseline 3.

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+resource ('Check whether a credential name is valid and free to use') and names the resource scope ('in the organisation'). It is clearly distinguishable from siblings like create_credential, get_credential, list_credentials and delete_credential without needing their schemas.

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 'candidate credential name' and 'free to use in the organisation' imply this is a pre-creation availability check, which is useful contextual framing. However, it never explicitly says when to use this versus alternatives (e.g., before create_credential) and names no sibling, so 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.