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

With no annotations provided, the description carries the full burden. It discloses that paid fields are removed, explains the canonical URL behavior, and warns against constructing URLs from event_id or slug. It also clarifies the distinct nature of external_url for broadcasts/streaming services, which is valuable behavioral context beyond a simple read operation.

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 front-loaded with the core purpose in one sentence. The subsequent paragraph about URL usage is detailed but focused on critical pitfalls, and there is no redundant filler. It earns its length given the importance of the usage caveats.

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?

Even without an output schema, the description explains the most important output fields (url and external_url) and how they should be handled. It could be more complete by describing the overall response structure or behavior when no events exist, but for a simple preview tool with one optional parameter, it is largely sufficient.

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 already provides 100% coverage for the single date parameter, including its pattern and default behavior. The description adds no further parameter-level details, so the baseline score of 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?

The description opens with a specific verb phrase, 'Preview up to three events for a Japan date with paid fields removed,' which clearly defines the action, resource, and scope. This distinguishes it from sibling tools list_capabilities and list_supported_competitions, which serve obviously different purposes.

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 implicitly clarifies when to use the tool (for previewing a date's events) and even provides detailed usage instructions for citing URLs. However, it does not explicitly state when not to use it or contrast it with alternatives, so it stops short of a full 5.

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