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

Annotations already declare a non-read-only, non-idempotent, open-world write, and the description usefully adds a 10-credit cost and the concrete POST endpoint. However it omits behavior an agent needs for a mutation: whether repeat calls create duplicate subscriptions (relevant given idempotentHint=false) and whether the receiving URL must be reachable or authenticated.

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 trigger condition is front-loaded in one short sentence and the bracketed metadata lines are scannable rather than verbose. It is efficiently sized, though the bracket block carries endpoint/cost data that arguably belongs in structured fields.

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?

An output schema exists, so return values need no explanation, and the cost and endpoint are present. Still, for a webhook-registration tool the definition leaves out the lifecycle story — duplicate handling, deletion via the webhooks_id siblings, and delivery expectations — which matters at this complexity.

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 67%, and the schema itself documents `fields` and `precision` in detail while `url` is covered only by the bare '[Required: url]' note. The description adds no meaning to the compaction parameters or any constraint on the callback URL beyond what the JSON schema already states.

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 names a concrete event trigger — Mercury through Pluto stationing direct — which is specific enough to distinguish it from the sibling astroway_webhooks_retrograde_start. It does not explicitly say the tool registers a webhook (that only comes from the title), and it never names the reciprocal sibling, so it falls short of a 5.

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?

There is no guidance on when to choose this registration endpoint versus astroway_webhooks_subscribe, astroway_webhooks_transit_trigger, or the retrograde_start variant. The bracketed metadata gives the required field, endpoint and cost, but neither exclusions nor prerequisites such as whether the URL must be verified first.

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