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

Beyond the readOnly/idempotent annotations, the description discloses important behavioral guarantees: it handles overnight shifts and DST, and it never contacts participants. This adds meaningful side-effect and edge-case context.

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 compact and well structured: it states the main action, key inputs, supported edge cases, and a negative guarantee in two sentences. No redundant wording is present.

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?

The description covers purpose, edge cases, and side-effect avoidance, but it omits output details and fails to reconcile the stated inputs with the empty input schema. This leaves an important contextual gap for an agent trying to invoke the tool 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?

The input schema is empty, yet the description claims the tool uses 'explicit IANA time zones and dates.' This implies parameters that are not defined in the schema, and the description does not provide their names, types, formats, or example values. The parameter information is therefore incomplete and potentially misleading.

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's purpose: finding overlapping working hours. It also specifies the key inputs ('explicit IANA time zones and dates') and distinguishes the behavior from related phone-number tools by emphasizing it never infers location from phone numbers.

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 useful usage criteria: use explicit time zones and dates, and it explicitly warns against using this tool when only phone numbers are available. However, it does not mention alternative tools or provide a fuller when-to-use/when-not-to-use contrast.

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