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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so safety is covered. The description adds genuine non-obvious behavior: the word 'real' implies live availability, and the closing note explains that times are not held by this call — the checkout page holds a slot for 7 minutes — which is exactly the kind of lifecycle context annotations cannot convey.

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 the core purpose, then three tightly parallel mode clauses, then the holding caveat. Every sentence carries distinct information and nothing is repeated from the schema.

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?

For an 8-parameter, no-output-schema tool this is nearly complete: it explains what each input mode returns (open dates, or start times with prices) and the 14-day cap, compensating for the absent output schema. It does not cover failure modes such as an invalid or unserviceable postal code, which keeps it from a 5.

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 and the schema already documents every parameter's format, enum, and default. The description goes beyond it by explaining the interaction between date and end_date and by noting that a date-only lookup returns times with their price, adding cross-parameter semantics the schema does not express.

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 ('Find real open dates, or start times ... for a booking at a postal code') and immediately signals the distinguishing scope of the tool. An agent can tell it apart from find_services, get_quote, and request_booking without opening a schema.

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?

It maps the three parameter combinations to three distinct behaviors (no date = next 14 days of dates; date only = that day's times; date + end_date = dates in range, max 14 days), which is effectively a when-to-use guide. It never names a sibling alternative such as find_services or get_quote, so it stops short of explicit routing.

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