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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, covering the safety profile. The description adds value by detailing the error handling behavior ('never raises a protocol error – returns an error object') and retry safety. It also shows a sample output with the verdict key for no-overlap cases. Minor deduction: the description could mention the local_windows format more precisely, but this is already covered by the output schema.

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?

The description is about 150 words – somewhat verbose but every part earns its place. It is front-loaded with the core purpose and free offering. Minor deduction: the description could be tightened slightly (e.g., 'FREE' could be integrated into the first sentence or omitted), and the error handling explanation is slightly redundant with the example. Still, it is well-structured and clear.

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 the tool's moderate complexity (3 parameters, 1 required, 100% schema coverage, output schema present), the description covers all essential aspects: purpose, input format with examples, output format with examples, success and no-overlap cases, error handling, retry safety, and alternatives. No gaps remain for an agent to misinterpret the tool.

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 the baseline is 3. However, the description adds substantial meaning: it shows typical input format as a JSON snippet, explains what offsets_utc means ('one UTC offset per participant'), clarifies work_start/work_end defaults, and gives an example return value. This goes well beyond what the schema provides by demonstrating usage patterns.

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 clearly states the tool finds shared meeting windows across time zones inside working hours. It distinguishes itself from siblings by explicitly noting it is not for converting a single time (business_days, sla_due likely handle date math) and not for expanding recurring series (recurrence_expand). The verb 'find the shared meeting window' plus resource 'time zones inside working hours' is specific and actionable.

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 explicitly says when to use this tool ('people in different zones need one shared slot') and when not to ('not for converting a single known time... not for expanding a recurring series'). It names the alternative recurrence_expand directly. This provides complete guidance for an agent to select the correct tool.

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