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

The description explicitly labels the operation as a WRITE operation, instructs the agent to confirm with the user, and notes idempotency. These add behavioral context beyond the annotations (readOnlyHint: false, destructiveHint: false), which only imply mutation. This is useful for an agent deciding how to present the action to a user.

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 tight and front-loaded: it opens with the core action, then lists the required parameter, optional parameter, and behavioral warnings. Five short sentences are slightly choppy but every sentence earns its place. No redundant 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 simple two-parameter write operation, the description covers the essential context: who performs the action, what is required, the write nature, confirmation requirement, and idempotency. It does not describe return values, error cases, or capacity checks, but with only two parameters and annotations present, this is adequate.

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 contains 100% parameter coverage with descriptions for both event_id and quantity, including the default of 1. The description adds no additional semantic detail beyond echoing 'Requires event_id' and 'default 1', so it stays at the baseline for schema-covered parameters.

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 uses a specific verb and resource: 'Registers the authenticated user for a school event.' This clearly distinguishes the tool from siblings like create_event (which creates an event) and cancel_event (which cancels an event). The phrase 'Requires event_id' further clarifies the primary input needed.

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 defines when to use this tool: whenever an authenticated user needs to register for a school event. It provides clear context and prerequisites ('Requires event_id') but does not explicitly name alternatives or state when not to use them. This is solid context without exclusion criteria.

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