CallMCP — Phone Call MCP Server

Set Webhook

set_webhook

Destructive

Create or update a business outbound webhook (URL + subscribed events). Returns a webhook secret on first creation only.

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": {
      "webhook_url": "<webhook_url>"
    },
    "name": "set_webhook"
  }
}

Input Schema

Name	Required	Description
`id`	No	Existing webhook ID to update (omit to create new).
`events`	No	Event types to subscribe to (get_webhook lists the supported types).
`preset`	No	Start the body from a CRM field map. Presets are editable starting points, not exact vendor formats. Ignored when payload_template is also sent.
`is_active`	No	Enable or disable delivery.
`body_format`	No	json (default) or form (application/x-www-form-urlencoded, nested keys flattened with dots).
`business_id`	No	Business ID (optional only when the token can access exactly one business).
`description`	No	Human label for this webhook.
`http_method`	No	HTTP method for delivery (default POST).
`webhook_url`	Yes	HTTPS/HTTP destination URL for event delivery.
`custom_headers`	No	Extra headers the CRM needs, as { "Header-Name": "value" } (max 20). A null value keeps the saved value for that name. Content-Type, Host, Content-Length and X-KaiCalls-* cannot be set. Values are never returned.
`payload_template`	No	Shape the body for a CRM: { "fields": { "<their field>": "<path>" \| { "value": <fixed> } } }. A path reads the standard event body (e.g. "data.phone", "occurred_at"); "a\|b" takes the first with a value; a dot in the field name nests it ("contact.phone"). Missing paths send null. null restores the standard body.

Output Schema

Name	Required	Description
`error`	No	Present when success is false
`events`	No
`message`	No
`success`	Yes	Whether the tool completed successfully
`webhook`	No
`business_id`	No
`webhook_secret`	No

Schema Changelog

Changes observed during successful MCP inspections.

First observedNov 12, 2026

TDQS

B3.3/5.0

Behavior3/5

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

Annotations already declare destructiveHint=true, openWorldHint=true, idempotentHint=false, and readOnlyHint=false, so the safety profile is largely covered. The description does add one genuinely useful non-obvious fact: the webhook secret is returned on first creation only. It does not explain what an update overwrites, whether custom headers are replaced or merged, or any auth/permission requirements, so it stops short of rich disclosure.

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 short sentences, front-loaded with the action and resource, then the one behavioral caveat that matters most. Nothing is repeated or wasted.

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?

For an 11-parameter destructive mutation with full schema coverage, an output schema, and rich annotations, the description is minimally sufficient. However, it omits the routing guidance an agent needs when several webhook tools exist, and it leaves the overwrite semantics of the update path unstated.

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 description coverage is 100% and all 11 parameters, including enums for preset, body_format, and http_method, are documented in the schema itself. The description only summarizes "URL + subscribed events", adding no syntax, defaults, or interaction rules beyond what the schema already states. Baseline 3 applies when the schema does the heavy lifting.

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

Purpose4/5

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

States a specific verb pair and resource: "Create or update a business outbound webhook (URL + subscribed events)". The parenthetical scopes the resource to outbound delivery, and the create-vs-update duality is explicit. It does not distinguish itself from siblings such as delete_webhook or get_webhook, which keeps it off a 5.

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 only usage signal is implicit: create versus update is controlled by the id parameter, which the schema explains rather than the description. There is no statement of when to prefer this tool over delete_webhook, get_webhook, or request_transcript_webhook, and no prerequisites or exclusions are given.

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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