Start here: what Hermoso can do and what it costs

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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint: false, so the safety profile is covered. The description adds valuable behavioral context beyond annotations: it is free and read-only, it reveals the full set of capability data returned, and it clarifies the non-requirement for rendering. It could note whether the response is cached or real-time, but the annotation coverage makes this a minor gap.

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?

Extremely efficient: two sentences pack purpose, timing, exclusions, and behavioral traits without any filler. Front-loaded with the core action and result set.

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 zero parameters and no output schema, the description fully covers what the agent needs: what it returns, when to use it, when not to, and that it is free/read-only. No critical gaps remain for correct invocation.

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 has zero parameters, so the baseline is 4. The description adds meaningful context about what information the probe returns, which compensates for the lack of a formal output schema and helps the agent know what to expect. No additional parameter details are needed since none exist.

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?

State a specific verb (Probe) and resource (what this Hermoso account can do), and enumerates exactly what is returned: model ids, credit costs, aspect ratios, video durations, recipe ids, and canEdit/canAvatar flags. This distinguishes it from siblings like generate_image and hermoso_credits.

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 call it ('when you need a specific model id, an exact cost, or a capability you are not sure of') and when NOT to call it ('It is NOT a prerequisite for rendering: generate_image, generate_video and render_ad all run with model omitted and route to the server’s own default'). This is exactly the kind of routing guidance that prevents wrong tool selection.

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