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

The annotations already establish write semantics (readOnlyHint=false), open-world behavior, and non-idempotency, so the bar is lower. The description adds genuinely useful context the annotations lack: the cost (10 credits, Tier 1), the HTTP endpoint, and the required field. It omits what actually matters for a webhook — delivery payload format, retry behavior, and whether repeated registrations for the same URL create duplicates (relevant given idempotentHint=false) or how to remove the webhook.

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 firing condition is front-loaded and the bracketed metadata block is scannable with no filler prose. The budget is well spent, though the group/endpoint lines carry limited decision value for the agent.

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 schema documents `fields` and `precision`. However, for a webhook-registration tool the description leaves the payload contents and lifecycle (creation vs. deletion) unexplained, which is the main gap an agent would hit.

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 single undocumented parameter is `url` — the only required one. The description merely repeats '[Required: url]' from the schema and says nothing about constraints (HTTPS-only?), what the callback will receive, or how `fields`/`precision` apply to the webhook payload rather than to a one-off response.

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 the triggering condition precisely ('Fires when any of Mercury–Pluto stations retrograde') but never says the tool *registers a webhook* — that verb+resource only appears in the title and the endpoint path. It also does not distinguish itself from astroway_webhooks_retrograde_end or astroway_stream_retrograde_alerts, so the agent must infer the action from structured metadata.

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 when-to-use or when-not-to-use guidance. The description does not say to prefer this over astroway_stream_retrograde_alerts when a persistent callback is wanted, nor does it mention any prerequisite beyond the '[Required: url]' tag.

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