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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so the safety profile is covered. The description adds genuine value beyond them: the exact fallback payload (Mon–Fri 09:00–17:00 UTC) and the presence of a `fallback: true` marker, plus the instruction to caveat the response. Pagination and error behavior are not mentioned, but there is little to page through here.

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?

Two sentences, front-loaded with the primary action and output shape, then the fallback caveat. No redundant restatement of the title, no filler, and the operational instruction (caveat the response) lands where the agent will read it.

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?

With an output schema present, the description need not explain return structure, and it covers the one non-obvious behavior — the silent fallback. The remaining gap is sibling disambiguation against availability.read, which matters given a crowded tool namespace but is not strictly needed to invoke this 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?

Schema coverage is 100% and the single `date` parameter already carries an ISO format note and the today-in-user's-timezone default. The description repeats the default without adding syntax, bounds, or edge-case guidance (e.g. dates outside configured workdays), so it matches the baseline for a fully documented schema.

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 — 'Read the invoking user's working-hours schedule' — and enumerates what comes back (work interval for a date, workdays list with 0=Sun…6=Sat encoding, timezone). That is far more specific than the title alone. It does not, however, distinguish itself from the sibling availability.read, so an agent cannot tell from this description alone which of the two to call.

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?

Offers an implicit default ('today by default') and a clear conditional behavior for unconfigured users, which helps the agent anticipate the common case. It never says when to prefer this over availability.read or working_hours.update, and gives no exclusion guidance, leaving routing to inference.

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