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

Annotations only carry idempotentHint and a title, so the description carries the real burden and delivers: idempotency keyed on URL, return of the signing secret, event-pattern matching semantics, and the hard constraint that deliveries originate from Volanea's servers so localhost/private addresses silently receive nothing. That is materially more than the annotations provide.

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?

Front-loaded with the core action and the returned secret, then the pattern and reachability caveats. Every sentence earns its place, though the tunneling sentence makes the whole thing a touch long for a single tool.

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?

With an output schema present, return values need not be detailed, yet the description still highlights the one output that matters (the signing secret). Event filtering, idempotency, and reachability caveats cover everything an agent needs to call this 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 coverage is 100%, so the baseline is 3; the description adds genuine meaning beyond the schema by noting idempotency is keyed on the URL and by spelling out that an omitted events array subscribes to everything. The public-reachability constraint on url is a semantic requirement the schema does not state.

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?

States a specific verb+resource ('Register an endpoint ... to receive Volanea events') and explicitly names the key return value (the whsec_ signing secret). It is clearly distinguishable from siblings like volanea_update_webhook_endpoint and volanea_test_webhook_delivery.

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?

Gives strong when-to-use context: explains why you register (to write signature verification), how events filter (patterns or omit for all), and the crucial public-internet constraint with concrete tunneling advice. It does not explicitly route to the update/delete siblings for modifying an existing endpoint, so it stops short of full alternative coverage.

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