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

The description discloses rich behavioral semantics beyond the annotations: idempotent upsert behavior, rescheduling, cancellation, timezone interpretation, and response details about WhatsApp known-contact status. Annotations only provide readOnly/destructive hints, so this description carries the behavioral burden and does it well. No contradiction.

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?

Four dense sentences, each earning its place: purpose, idempotency/semantics, timezone rule, and response hint. The content is front-loaded and there is no fluff.

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 9-parameter mutation tool with no output schema, the description covers the core behavioral contract and at least part of the response. It does not fully describe the response shape, but it highlights the one decision-relevant output (known-contact status). Combined with the schema's parameter details, this is sufficiently complete 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 description adds meaning beyond the schema for key parameters: external_id drives update semantics, start_at drives rescheduling and timezone handling, status 'cancelled' drives cancellation. Schema coverage is 56%, and several parameters like service, client_name, and confirm are left to the schema, but the most behaviorally important parameters are well explained.

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 states a specific verb and resource: 'Record a booking made outside the assistant so the platform confirms it and reminds the client.' It clearly distinguishes an upsert workflow from the sibling list/get tools, and the title 'Create or update a booking' reinforces the semantic.

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 description gives clear context for when to use this tool and explains behavioral variants: same external_id means update, new start_at means reschedule, status 'cancelled' means cancel. It does not explicitly name sibling alternatives or say when not to use it, but the use case is concrete enough for an agent to route correctly.

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