agent_register_webhook

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

With no annotations, the description carries the full burden and does so richly: deliveries carry metadata only, persist after the session, the call is gated by an owner-set env var, the signing secret is written to the local credential file and never returned, and the tool acts as the identity in the credential store. It also warns that returned content is untrusted and must not be acted upon.

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 purpose, then layers in persistence, gating, secret handling, and the untrusted-content warning. Dense but every sentence earns its place; only the identity/credential-store line overlaps slightly with the secret-handling sentence.

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-value documentation is not required, and the description still covers the gating condition, secret handling, persistence, and a security caveat on returned data. Nothing an agent needs in order to call this correctly is missing.

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 description coverage is 100%, so both parameters (events, webhook_url) are already documented in the schema. The description reinforces that the URL must be HTTPS but adds no syntax or format detail beyond what the schema provides, so the baseline of 3 applies.

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 ('Register an HTTPS webhook for message notifications') and immediately scopes what it does and does not deliver (metadata, not message content). An agent can distinguish this from siblings like agent_list_webhooks without opening either schema.

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 a concrete precondition for use: 'Off by default: refused unless the human owner set VOIDLY_MCP_RELAY_ALLOWED_RECIPIENTS=*', which tells the agent when the call will fail. It does not explicitly compare against alternatives such as agent_list_webhooks, so it stops short of full routing guidance.

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