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

Annotations supply only destructiveHint=true; the description earns credit by disclosing partial-update semantics (PATCH, unspecified fields preserved), which materially reduces the risk of accidental data loss on a destructive tool. It stops short of noting permission/auth requirements, whether cancelling is reversible via this same call, or any rate limits.

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 sentences, zero filler, and the most important signal (MUTATES) is the very first word. The endpoint/body-format notes and the fields-passthrough hint follow in descending order of importance.

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 10-parameter destructive mutation with no output schema, the description covers what changes, how (partial PATCH), where the id goes, and how to pass undocumented fields. The remaining gap is sibling routing versus youcanbookme_cancel_booking and the absence of any success/return indication.

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 100%, so baseline is 3; the description mostly restates schema property names (title/startsAt/endsAt/cancelled/noShow/timeZone/locale/units). The one genuinely additive note is that the path id is never sent in the body, plus the reminder that `fields` is merged over the typed fields — though the schema already says that for `fields`.

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?

Opens with a specific verb and resource ("MUTATES ... updates an existing booking") and enumerates the concrete intents: reschedule, rename, mark cancelled/no-show. That is enough for an agent to separate it from youcanbookme_create_booking, youcanbookme_get_booking and youcanbookme_list_bookings without opening a schema.

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?

Gives real operating context: it is a PATCH partial update, so only supplied fields change, and the `fields` passthrough is the escape hatch for answers/linkFields or other documented fields. It does not, however, route the agent against the overlapping sibling youcanbookme_cancel_booking (which this tool can also do via cancelled=true) or state when not to use it.

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