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

Annotations already establish that this is a read-only, idempotent, non-destructive operation, so the safety profile is covered. The description adds the meaningful behavioral fact that this returns static specification content (a scheme and handshake) rather than live per-endpoint state, which is what an agent needs to decide whether to call it.

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?

One sentence, front-loaded with the verb and resource, with the enumerated contents and the caller benefit packed into the same clause. Nothing is padded and nothing is redundant with the title.

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 not be explained, and annotations cover the safety profile. For a zero-parameter documentation tool the description is essentially complete, though it could note whether the content is static/versioned spec text versus server-specific configuration, which would matter to a caller implementing verification.

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?

The tool takes zero parameters, which is the baseline-4 case per the rubric. The empty schema and the description's framing agree that no input is required, and no parameter semantics are needed.

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 specific verb ("Describe") and a precise resource (the Standard Webhooks signing scheme), then enumerates the exact contents: headers, HMAC-SHA256 algorithm, envelope shape, replay tolerance, and the url_verification handshake. It is unmistakably distinct from sibling tools like kellian_discover_events or kellian_list_webhook_event_types, which enumerate events rather than explain signing.

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 phrase "so a receiver can verify deliveries without reading source" gives a clear use context — implement or validate a webhook receiver. It stops short of explicit routing guidance (e.g., "call this before registering an endpoint; use list_webhook_event_types to choose subscriptions"), so no true exclusions or alternatives are stated.

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