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

The description explicitly warns that this is a WRITE operation and instructs the agent to confirm with the user before signing up. It also discloses idempotence, which goes beyond the readOnlyHint/destructiveHint annotations and adds meaningful behavioral context.

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?

Three short sentences deliver the main action, required parameter source, and a critical side-effect warning with no filler. Every sentence earns its place and the most important caveat is clearly highlighted.

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 single-parameter write operation, the description covers the core action, how to obtain the required ID, user confirmation, and idempotence. An output schema is present, so return-value detail is not needed. 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 only says shift_id is a 'Volunteer shift ID,' but the description adds provenance: the ID comes from get_upcoming_events or event detail. This gives the agent practical guidance on sourcing the parameter beyond the schema's minimal definition.

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 and resource: 'Signs up the authenticated user as a volunteer for a specific shift.' It clearly identifies the action and scope, and there is no close sibling tool with overlapping purpose. The mention of shift_id source further anchors what the tool does.

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 gives clear context for use by requiring shift_id from get_upcoming_events or event detail. It does not name alternatives, but none of the sibling tools compete with this volunteer signup action, so the guidance is effectively complete for routing.

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