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

Annotations cover the safety profile (readOnlyHint=true, destructiveHint=false), so the bar is lower. The description adds genuine behavioral context beyond that: slots are live and can be taken at any time, so results go stale, and the response attribution links to a contact page for direct booking.

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 what the tool returns and its constraints, then the booking handoff and the freshness warning. Dense but every sentence carries operational value; no filler.

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?

An output schema exists so return-value explanation isn't required. The description still completes the workflow picture: timezone, weekday constraint, locale behavior, booking handoff, and staleness warning. Nothing an agent needs to route or call correctly 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 100%, so the baseline is 3. The description goes further by explaining how to use maxSlotsPerDay in practice (a sample spread across the day, default 8) and the specific re-call pattern with days:1 and maxSlotsPerDay:32 for a targeted time, which is not derivable from the schema alone.

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?

States a specific verb (lists) and resource (open appointment slots) with scope details: free, non-binding, 15-minute initial phone call, weekdays, Europe/Berlin, grouped by day. An agent can instantly distinguish this from book_appointment and the unrelated calculation siblings.

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?

Explicit routing: for a specific time, re-call with days:1 and maxSlotsPerDay:32; to book, pass startDateTime unchanged to book_appointment; and re-check rather than reusing an old list. The alternative (book_appointment) and the conditions selecting each path are named directly.

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