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=true and destructiveHint=false, and the description reinforces this with 'Read-only, free.' It adds meaningful behavioral context beyond the annotations: the operation is a live probe of current account capabilities, lists the specific response contents, and clarifies that it carries no credit cost and is not a required precondition for rendering.

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?

The description is four tightly packed sentences with no filler: it front-loads what the tool returns, then gives when to call it, then explicitly addresses a common false assumption about rendering prerequisites, then closes with safety/cost signal. Every sentence 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 has no parameters and no output schema, the description carries the full burden of explaining what comes back, and it does: model ids, credit costs, aspect ratios, video durations, recipe ids, and capability flags. It also covers cost, safety, and relationship to sibling generators, making the tool fully actionable without additional lookup.

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 tool accepts zero parameters and schema description coverage is 100%, so there is no parameter documentation burden. The description accurately treats it as a no-input probe, and any parameter semantics would be irrelevant here.

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 ('Probe') and a clear resource: what the Hermoso account can do right now, enumerating exactly the data returned (model ids, credit costs, aspect ratios, durations, recipe ids, flags). It also distinguishes itself from rendering siblings by explicitly stating it is not a prerequisite for generate_image, generate_video, or render_ad.

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?

It gives explicit trigger conditions: 'Call it when you need a specific model id, an exact cost, or a capability you are not sure of.' It also provides an exclusion and names the alternatives: rendering tools run fine with model omitted and route to the server's default, so agents know not to call this as a prerequisite.

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