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

Annotations already declare readOnlyHint=true and idempotentHint=true, so the safety profile is covered. The description adds useful behavioral context: stays are fixed 7-day weeks, arrival must be a Saturday, non-Saturday dates are rejected, and only venues with real availability are returned. It doesn't detail pagination or exact response shape, but for a read-only lookup tool this is strong.

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 front-loaded: it states the core purpose in the first sentence, then adds the critical date-format constraint, then the return behavior, then the sibling differentiation. Every sentence earns its place with no filler.

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 lookup tool with 100% schema coverage and no output schema, the description covers the essential context: what it returns, the date constraints, the default behavior, and when to use it instead of list_venues. It could mention whether results are sorted or limited, but nothing critical is missing for an agent to call it 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 description coverage is 100%, so the schema already documents all four parameters. The description adds value by explaining the relationship between date and month (mutually exclusive modes), the Saturday constraint, and the default-to-current-month behavior, which goes beyond the schema's individual parameter descriptions.

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 states a specific verb ('Check'), a specific resource ('Angling Lines venues'), and a precise scope ('genuinely have space for a party'). It also explicitly distinguishes itself from list_venues, making it clear this is the availability-checking tool, not the general listing tool.

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 'Use this — not list_venues — whenever the question is about what is free or bookable.' It also explains the two modes (single Saturday vs whole month) and the date format requirements, giving clear when-to-use guidance and naming the alternative.

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