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

Annotations already declare the write-ish, open-world, non-idempotent, non-destructive profile, so the bar is lower, and the description does add real context the annotations lack: the POST endpoint and a 10-credit cost. However, it says nothing about delivery semantics, whether re-registering duplicates a subscription, how the URL is verified, or how to remove the webhook, which matters for a non-idempotent open-world mutation.

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 one-sentence purpose plus bracketed metadata block is compact and front-loaded, with no filler. The tradeoff is that the tag-style layout spends four lines on endpoint/group/required/cost while omitting behavior, so the structure is efficient but thinly informative.

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 shape need not be explained, but for a webhook registration tool the description leaves the important questions open: what a threshold-crossing event contains, delivery guarantees, URL requirements, and lifecycle/unsubscribe path. With openWorldHint true and idempotentHint false, the missing guidance on repeat subscription and cleanup is a meaningful gap.

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?

'[Required: url]' only restates the schema's own required list and adds no constraint (e.g., must be publicly reachable, HTTPS, verification handshake). The two optional compact-mode parameters, fields and precision, are documented in the schema but receive no mention or framing in the description, leaving the 67% coverage uncompensated.

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?

'Subscribe to natal-transit aspect threshold-crossings' names a concrete verb and a specific event stream, so an agent knows this registers a webhook rather than streaming or fetching. It does not differentiate itself from nearby siblings such as astroway_webhooks_subscribe or astroway_stream_transit_alerts, which is the only thing keeping it from 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?

The description gives no when-to-use or when-not-to-use guidance, and never mentions the alternative webhook siblings or the streaming equivalents that could cover similar needs. The only selection signal is the tool name and the bracketed group/endpoint metadata, which is implied rather than stated.

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