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

Annotations already declare readOnlyHint=false, idempotentHint=false, openWorldHint=true, destructiveHint=false, so the safety profile is covered. The description adds two genuinely useful facts beyond structured data: expected frequency (24/day) and cost (10 credits, Tier 1). It does not disclose auth requirements, or what happens on duplicate registration for a non-idempotent create.

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?

Very compact and front-loaded: the trigger frequency leads, followed by terse Group and Cost metadata. No wasted prose, though the cost/group tags are bracketed metadata rather than explanatory text.

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 non-idempotent registration mutation with 40+ sibling tools, the description omits what the tool actually creates, auth/prerequisite needs, and any differentiation from sibling webhook tools. An output schema exists so return values need no explanation, but the missing action verb and usage routing leave real gaps.

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%; the required 'url' parameter has no description in either the schema or the description. 'fields' and 'precision' are well documented in the schema itself, so the description adds no parameter value and leaves the one mandatory argument completely unspecified.

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 event trigger ('Fires at every planetary hour boundary (24/day)') but never states the action the tool performs, which is registering a webhook. The verb is only implied by the tool name and title. An agent can infer it from 'astroway_webhooks_*' naming, but the description itself describes the webhook's firing behavior rather than what this call 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?

No guidance on when to use this versus the many sibling webhook/subscription tools, including the near-neighbor astroway_stream_planetary_hour_changes. No prerequisites (auth, existing subscription, deduplication) are mentioned. The Group tag hints at the family but routes nothing.

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