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

Goes well beyond the annotations (destructiveHint=true, idempotentHint=false) by disclosing that the HMAC secret is returned only once, that delivery is best-effort with a specific 3-attempt retry schedule (immediate, 500ms, 2s), that HTTP 2xx terminates the loop, that non-public targets are not retried, and that each attempt has a 5s socket timeout. This is exactly the operational context an agent needs and no annotation contradiction exists.

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-loads the registration purpose and inputs, then layers limits and delivery semantics in short declarative sentences. Dense but each sentence carries operational value; the trailing docs URL is the only filler.

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 mutating, non-idempotent registration tool with no output schema, the description covers quotas, target restrictions, retry/timeout behavior, and return values (webhook id plus one-time HMAC secret). An agent can call it correctly without consulting external docs.

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 url, token, and events are already fully documented, including enum values and 'omit for all'. The description restates the inputs and adds plan limits, but does not add syntax or clarify the distinction between the input bearer token and the returned HMAC secret beyond what the schema provides.

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 ('Registers') and resource (an http/https URL for a webhook) plus the exact event set, so an agent immediately distinguishes it from list_webhooks and delete_webhook. The scope of what is being created is unambiguous.

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?

Gives practical preconditions: plan-based webhook quotas (1/5/20) and the rejection of private, internal, and localhost targets. It does not explicitly name sibling alternatives or say when to use list_webhooks/delete_webhook instead, but the creation framing makes those choices obvious.

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