machine-inbox

set_webhook

Register or replace the inbox webhook: an HMAC-signed POST fires on every inbound message with metadata, extracted verification codes, and injection risk (never the body). Returns the signing secret.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "inbox_id": "<inbox_id>",
      "url": "<url>"
    },
    "name": "set_webhook"
  }
}

Input Schema

Name	Required	Description
`url`	Yes	Public https URL that receives the signed POST.
`token`	No	Mailbox bearer token (mi_live_...) returned when the inbox was purchased. Optional when the MCP request itself carries Authorization: Bearer.
`inbox_id`	Yes	Inbox UUID.

Schema Changelog

Changes observed during successful MCP inspections.

AddedAug 18, 2026

TDQS

A3.8/5.0

Behavior4/5

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

With no annotations, the description carries full burden for behavioral disclosure. It accurately describes the side effect: a signed POST to the URL on every inbound message, with specific payload contents and the exclusion of the body. It also states the return value. Missing details about authorization requirements or error states, but overall transparent for a webhook creation tool.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Two sentences with no wasted words. The first sentence front-loads the purpose and explains the triggered behavior, the second specifies the return value. Every sentence earns its place; no repetition or filler.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Despite no output schema, the description covers the return value (signing secret) and the webhook's behavioral contract. It explains what triggers the POST and its payload. Missing explicit mention of error responses or ordering dependencies (e.g., inbox must exist beforehand), but for a registration tool this is largely complete.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% with all three parameters described in the input schema. The tool description does not add further meaning to the parameters beyond what the schema already provides. Baseline score of 3 is appropriate because the schema already handles parameter semantics adequately.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool registers or replaces an inbox webhook, specifying the triggered POST behavior (HMAC-signed, contains metadata/verification codes/injection risk, never body) and return value (signing secret). This distinguishes the tool from its siblings like get_webhook (read) and delete_webhook (removal).

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description does not provide explicit guidance on when to use this tool vs. alternatives. It says 'register or replace' but does not direct the agent to use get_webhook to check existing webhooks or delete_webhook to remove them. No context about prerequisites or ordering relative to other tools like create_inbox.

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

All machine-inbox tools Inspect

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