trmnl_get_room_booking_billing

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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description adds real context beyond them: billing is per-calendar, monthly or yearly after a trial, and Stripe sessions can only be opened by the owner in a browser. That constraint is exactly the kind of behavioral fact an agent would otherwise get wrong. It does not describe the full shape of the returned billing state, keeping it off a 5.

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?

Three short sentences, front-loaded with the purpose before the billing-model context and the raw endpoint. The endpoint line is mildly redundant but cheap and useful for orientation. Nothing is padded.

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 read-only tool with no output schema, the description supplies the necessary framing: what billing state means here, that it is per-calendar, and that checkout_url/portal_url are the actionable outputs. An agent can call it correctly and interpret the result without further context.

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?

Schema coverage is 50%, and both parameters (installation_id, profile) already carry their own descriptions in the schema. The description only embeds installation_id in the endpoint path and says nothing about what 'profile' means or how profiles affect the billing lookup, so it adds little over the structured data. 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 first sentence names a specific verb and resource — 'Read the billing state of a room booking installation' — which cleanly separates it from the many other room-booking siblings (get_room_booking, get_room_booking_settings, list_room_booking_calendars). It never explicitly names a sibling it is not, so it stops short of a 5.

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 draws a clear boundary: subscribing and managing the subscription happen in the browser via checkout_url/portal_url, and 'the API never starts one.' That tells the agent when this tool's job ends and an out-of-band action begins, which is strong guidance for a read-only tool. There is no explicit 'use X instead' alternative, since no sibling covers billing.

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