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zebbern

Webhook.site MCP Server

by zebbern
OverviewSchemaRelated ServersScoreDiscussions
Python
Remote

check_for_callbacks

Check if SSRF, XSS, or canary callbacks arrived in the last N minutes. Use after generating payloads or tokens to confirm delivery.

Instructions

See if SSRF, XSS, or canary callbacks arrived in the last N minutes.

    Use after generate_ssrf_payload / generate_xss_callback / generate_canary_token.
    For a website verification email, use wait_for_email.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
identifierNo
since_minutesNo
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. Changed11 schema fields changedv2.2.2
    • addedInput schema / properties / identifier / anyOf
      Added value: +[
+  {
+    "type": "string"
+  },
+  {
+    "type": "null"
+  }
+]
    • addedInput schema / properties / identifier / default
      Added value: +null
    • removedInput schema / properties / identifier / description
      Removed value: -"Filter for specific identifier in request URL/content"
    • addedInput schema / properties / identifier / title
      Added value: +"Identifier"
    • removedInput schema / properties / identifier / type
      Removed value: -"string"
    • removedInput schema / properties / since_minutes / description
      Removed value: -"Only check requests from the last N minutes (default: 60)"
    • addedInput schema / properties / since_minutes / title
      Added value: +"Since Minutes"
    • 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: +"check_for_callbacksArguments"
    • changedOutput schema / (root)
      Previous value: -nullNew value: +{
+  "additionalProperties": true,
+  "title": "check_for_callbacksDictOutput",
+  "type": "object"
+}
  2. Addedv2.0.3
  3. Removedv2.0.0
  4. First observedv2.1.3

TDQS

A4/5.0
Behavior3/5

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

No annotations are present, so the description is the sole source of behavioral context. It clearly implies a non-destructive check via 'See if ... arrived' and scopes it to callback types and a time window, but it does not explicitly state whether callbacks are consumed or whether this is a blocking vs. one-shot poll.

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?

Three short sentences place the primary behavior first, then usage context and an alternative. No filler or redundancy.

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

Completeness3/5

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

The existence of an output schema means return values do not need to be restated. The description gives workflow and alternative context, but the undeclared identifier semantics and low schema coverage leave a real gap for a 3-parameter tool.

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?

Only webhook_token has a schema description, so the description must compensate. It indirectly documents since_minutes ('last N minutes') but gives no meaning to the nullable identifier filter, which remains ambiguous.

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 uses a specific verb ('See if') and resource ('SSRF, XSS, or canary callbacks'), while time-window scoping differentiates it from generic request/email waiters. This is a distinct purpose among siblings.

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

Usage Guidelines5/5

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

It explicitly instructs to use after the three generate_* tools and names wait_for_email as the correct alternative for website verification emails. This is concrete when-to-use guidance with an exclusion.

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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