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

Annotations already declare write, non-idempotent, open-world behavior; the description goes further by disclosing the elicitation handshake, the manual-confirmation fallback, and the downstream effect (Cal.com emails a confirmation with reschedule/cancel links to the attendee address). It does not cover failure modes such as a slot being taken between get_availability and booking, which is the one behavioral gap for a booking tool.

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?

Front-loaded with the one-line purpose before procedural detail, and every sentence carries operative information (approval flow, required fields, downstream email). It is dense and the elicitation parenthetical is heavy, but the complexity of the two-mode flow justifies most of the length.

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 7 parameters, an output schema, and a multi-step conditional flow, the description supplies everything an agent needs: precondition (slot from get_availability), the two execution paths, and the required user-facing confirmation. Return values are covered by the output schema, so nothing material is missing.

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 high (86%), so the baseline is 3, but the description adds genuine meaning: 'start' is constrained to get_availability output, name/email must be the user's real values, and 'confirmed' is scoped to clients without elicitation. 'meeting_type' (the only enum) is still left unexplained, which holds it below a 5.

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?

Names the specific verb and resource ('Book a call with Jan Linketscher') and immediately establishes scope ('on behalf of your user'), which distinguishes it from the sibling read tools (get_availability, list_meeting_types). An agent knows exactly what this tool produces without opening the 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?

Explicitly requires that 'start' come from get_availability, names that sibling as the upstream step, and branches into two modes (elicitation form mode vs. manual approval with confirmed: true). It also gives an explicit prohibition ('never invent' name/email), leaving no ambiguity about when and how to call it.

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