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

Beyond the annotations, it discloses that all tickets go to the caller with no per-student split, that paid events debit the wallet, and that the call fails on insufficient balance, sold out, or closed registration. This significantly clarifies side effects; no statement contradicts the annotations, though the idempotentHint tradeoff is left to the annotation.

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 definition is compact and front-loaded: purpose first, then financial consequence, failure conditions, and sibling routing. The second sentence is dense but each clause earns its place.

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 two-parameter registration tool, the description covers purpose, ticket allocation, costs, failure modes, and alternative tool, while an output schema exists for return values. Nothing essential is missing.

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 schema covers 100% of parameters and already defines event_id and quantity; the description adds real semantic value by stating that quantity is tickets for the caller, enforces minimum 1, and explicitly rules out per-student splitting.

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 and resource: 'Registers the authenticated user for a school event and issues tickets to the caller.' It also differentiates itself from the volunteer sibling by explicitly directing volunteer use to sign_up_for_volunteer_shift.

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 names the key alternative ('To volunteer at an event rather than attend, use sign_up_for_volunteer_shift') and gives conditional guidance for paid events with 'confirm before registering.' Failure conditions (sold out, registration closed, insufficient balance) further clarify when a call would not be appropriate.

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