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

Goes well beyond the annotations (readOnlyHint=false, openWorldHint=true, non-idempotent, non-destructive) by disclosing that signing_secret is returned only once, the exact HTTPS POST payload shape, the per-delivery id dedupe rule, and the full HMAC verification contract with a 5-minute replay window. This is exactly the operational context an agent cannot infer from structured fields.

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 action, the event enum, and the one-time signing_secret warning, so the critical facts come first. It is a dense single paragraph, and the signature-verification algorithm could be segmented or moved to a docs pointer, but no sentence is truly wasted for a webhook 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?

For a 2-parameter tool with no output schema, the description effectively covers the return value (signing_secret, one-time) and the full downstream webhook contract. Remaining gaps are subscription lifecycle details such as limits, auth requirements, and error behavior on an invalid or unreachable callback URL.

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, but the description adds genuine meaning by spelling out what each event type delivers in its data payload (gamma_flip/spot, which/level, from/to), which helps an agent pick the right enum value. The callback_url parameter still gets no added semantics beyond the schema.

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 and resource (subscribe a callback URL to a market-structure event) and enumerates the three event types inline. The verb alone separates it from its siblings unsubscribe_event and list_subscriptions, though it never names an alternative explicitly.

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?

When-to-use is implied by the verb and the event enum, but there is no explicit guidance on when not to use it, how to remove a subscription (unsubscribe_event exists), whether duplicate subscriptions are permitted, or any prerequisite like the callback being publicly reachable over HTTPS.

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