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

Annotations already declare readOnlyHint=true, openWorldHint=true and destructiveHint=false, so the safety profile is covered. The description adds real value beyond them: it discloses the return shape (per-date start times, free spots, booked counts because there is no output schema) and states an auth prerequisite ('Needs the user's Cotlet API key with access to this app').

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?

Four short sentences, front-loaded with purpose and return contents, then usage and prerequisites. Nothing is padded, though the leading 'GetYourGuide:' brand prefix is redundant with the tool name and title.

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 a read-only, 3-param tool with no output schema, the description covers purpose, return fields, a pre-mutation usage trigger, and the auth requirement. What is missing is the return format detail (pagination/response envelope) and explicit routing to update_availability for the write case.

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 all three parameters (option_id, from, to) are already documented, including 'Option ID from list_products.' The description only echoes the date-range idea ('for the dates you ask for') and adds no format or semantic detail beyond the schema; 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 resource and scope: 'Start times and free spots of an option for the dates you ask for,' and elaborates the returned structure (dates, start times, free spots, booked count). It is clearly distinguishable from the write-side sibling by the 'before closing a slot' framing, though it never names update_availability explicitly, so sibling differentiation is inferred rather than stated.

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?

Provides a concrete usage context: 'Use it before closing a slot to see who is already booked.' This tells the agent when the tool is relevant (pre-mutation check) but does not explicitly name the alternative (getyourguide_update_availability) or any exclusions, so it stops short of a full when-to-use/when-not statement.

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