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

Annotations already declare readOnlyHint/idempotentHint/destructiveHint=false, so safety is covered structurally. The description adds real context beyond them: slot granularity (30 minutes), the UTC/ISO 8601 encoding of results, and the hard contract that returned values must be passed verbatim to book_call.

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 compact sentences, each earning its place: what it returns, how the output is formatted, how to use it downstream. The essential 'what' is front-loaded with 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?

No output schema exists, but the description compensates by specifying the result format (ISO 8601 UTC start times) and the downstream consumption contract. Combined with the fully documented input schema and safety annotations, an agent has everything needed to call it correctly.

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 description coverage is 100%, so days, from, and locale are already documented with defaults and bounds in the schema. The description adds nothing parameter-specific beyond confirming the return format, so the baseline 3 applies.

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 and resource ('List the open 30-minute slots for a free video call with Mike Fluff') and even scopes the subject matter (business diagnosis, AI automation, compliance, Architect Mode). An agent can immediately distinguish this from book_call or any other sibling.

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 sequencing guidance: 'Use before book_call; pass one of these exact values as its "slot"' tells the agent when to call and how the result feeds the next tool — unusually strong routing. It lacks an explicit when-not condition (e.g., skip if a slot is already known), so it falls just short of 5.

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