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zebbern

Webhook.site MCP Server

by zebbern

send_to_webhook

Send a JSON payload to a Webhook.site webhook to test that capture works.

Instructions

POST JSON to the webhook URL to test that capture works.

Use when the user wants to send a sample payload, not when they are waiting for a real site or email.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
dataYes
headersNo
webhook_tokenYesWebhook UUID returned by create_webhook

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault

No arguments

Schema Changelog

Changes observed during successful MCP inspections. Dates show when Glama detected each change.

  1. Changed12 schema fields changedv2.2.2
    • addedInput schema / properties / data / additionalProperties
      Added value: +true
    • removedInput schema / properties / data / description
      Removed value: -"JSON data to send to the webhook"
    • addedInput schema / properties / data / title
      Added value: +"Data"
    • addedInput schema / properties / headers / anyOf
      Added value: +[
      +  {
      +    "additionalProperties": {
      +      "type": "string"
      +    },
      +    "type": "object"
      +  },
      +  {
      +    "type": "null"
      +  }
      +]
    • changedInput schema / properties / headers / default
      Previous value: -{}New value: +null
    • removedInput schema / properties / headers / description
      Removed value: -"Optional custom headers to include in the request"
    • addedInput schema / properties / headers / title
      Added value: +"Headers"
    • removedInput schema / properties / headers / type
      Removed value: -"object"
    • changedInput schema / properties / webhook_token / description
      Previous value: -"The webhook token (UUID) from webhook.site"New value: +"Webhook UUID returned by create_webhook"
    • addedInput schema / properties / webhook_token / title
      Added value: +"Webhook Token"
    • addedInput schema / title
      Added value: +"send_to_webhookArguments"
    • changedOutput schema / (root)
      Previous value: -nullNew value: +{
      +  "additionalProperties": true,
      +  "title": "send_to_webhookDictOutput",
      +  "type": "object"
      +}
  2. Addedv2.0.3
  3. Removedv2.0.0
  4. First observedv2.1.3

TDQS

A3.5/5.0
Behavior2/5

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

There are no annotations, so the description must carry the behavioral transparency burden. It discloses that the tool POSTs JSON, but it does not explain side effects (e.g., whether a request record is created), authentication requirements, rate limits, or what the response contains. For a send/test mutation without annotations, this is too thin.

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?

The description is compact and front-loaded: the first sentence states the action, and the second gives practical usage guidance. Every sentence contributes value without unnecessary detail.

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

Completeness2/5

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

The tool has three parameters including a nested object and an output schema, but the description does not cover important operational details such as how headers are used, what the response represents, or the significance of webhook_token. It is adequate for a trivial test action but incomplete for a tool with this schema complexity and no annotations.

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

Parameters2/5

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

Schema description coverage is only 33%, and the description adds little beyond 'JSON'. It does not clarify the role of data, headers, or webhook_token, nor how they relate to the HTTP request. The schema helpfully describes webhook_token, but data and headers are left under-explained.

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 action: 'POST JSON to the webhook URL to test that capture works.' It also distinguishes this tool from related send/wait tools by mentioning 'sample payload' and contrasting with waiting for real sites or emails.

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

Usage Guidelines4/5

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

The description explicitly provides a when-to-use ('when the user wants to send a sample payload') and a when-not-to-use ('not when they are waiting for a real site or email'). However, it does not name alternative sibling tools, such as send_multiple_requests or wait_for_request, so it stops short of fully explicit alternatives.

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

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