Post Instances Webhook Endpoints

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

Goes beyond the annotations (readOnlyHint=false, destructiveHint=false, openWorldHint=true) by disclosing the HTTPS requirement, that deliveries are signed via Svix, and that every delivery should be verified. It does not cover auth/permission requirements, duplicate-URL behavior, or whether a signing secret is returned at creation.

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?

Three dense sentences with the core behavior front-loaded, then the event reference, then the security obligation. No 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?

No output schema exists, and the description never states what creation returns (endpoint id, signing secret, status) or that the secret must be fetched separately. Adequate for calling the tool, but thin for a mutation tool with a nested body and an idempotency parameter.

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 only 33% (only Idempotency-Key is documented). The description does add value by characterizing the URL as HTTPS and pointing to the events schema/MCP resource for the events array, but says nothing about instance_id or the URL constraints beyond the protocol.

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 ('Registers an HTTPS endpoint that receives the listed events'), which is unambiguously the create operation versus the Get/Delete webhook-endpoint siblings. An agent can identify the operation without opening the 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 clear post-creation steering: it points to the webhooks section / blindpay://webhooks/events resource for event names, and to Retrieve Webhook Secret for the signing secret. It does not explicitly state when to prefer this over listing or updating endpoints, but the operation type makes the choice obvious.

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