Chains

Chains are multi-step workflows that execute actions sequentially. Each step can be an HTTP call, a human approval gate, or a timed wait. Data flows between steps through variable interpolation.

Create Chain

POST /chains

Request Body

Field	Type	Required	Description
name	string	Yes	Chain name (max 255 chars)
steps	array	Yes	Step definitions (min 2, max 20)
input	object	No	Input variables available for interpolation in all steps
error_handling	string	No	fail_chain (default) or skip_step

Step Types

Every step requires a name, a type, and optionally a condition.

http_call step

Field	Type	Required	Description
name	string	Yes	Step name
url	string	Yes	Request URL
method	string	No	HTTP method (default: POST)
headers	object	No	Request headers
body	object	No	Request body
max_attempts	integer	No	Max delivery attempts (default: 5)
retry_strategy	string	No	exponential (default) or linear
condition	string	No	Expression that must evaluate to true for the step to run

gated step

Field	Type	Required	Description
name	string	Yes	Step name
gate.message	string	Yes	Approval request message
gate.recipients	array	Yes	Email addresses, phone numbers, or contact IDs
gate.timeout	string	No	Response timeout (e.g., 4h, 7d). Default: 7d.
gate.on_timeout	string	No	cancel (default), expire, or approve
gate.confirmation_mode	string	No	first_response (default) or all_required
gate.max_snoozes	integer	No	Max snooze count (default: 5)
condition	string	No	Expression that must evaluate to true for the step to run

delay step

Field	Type	Required	Description
name	string	Yes	Step name
delay	string	Yes	How long to pause (e.g., 5m, 1h, 2d)
condition	string	No	Expression that must evaluate to true for the step to run

Note: Responses return webhook, approval, wait as aliases for http_call, gated, delay respectively.

Variable Interpolation

Steps can reference input data and results from earlier steps:

• {{input.field}} -- Access values from the chain's input object
• {{steps.N.response.field}} -- Access the JSON response body of step N (zero-indexed)
• {{steps.N.status}} -- Access the outcome status of step N

Condition Operators

Operator	Description
==	Equal
!=	Not equal
>	Greater than
<	Less than
>=	Greater than or equal
<=	Less than or equal
contains	String contains substring
not_contains	String does not contain substring
starts_with	String starts with prefix
ends_with	String ends with suffix

Example condition: {{steps.1.status}} == 'confirmed'

Example

curl -X POST https://api.callmelater.io/v1/chains \
  -H "Authorization: Bearer sk_live_..." \
  -H "Content-Type: application/json" \
  -d '{
    "name": "Expense Approval Workflow",
    "steps": [
      {
        "name": "Submit expense",
        "type": "http_call",
        "url": "https://api.example.com/expenses",
        "method": "POST",
        "body": {
          "amount": "{{input.amount}}",
          "description": "{{input.description}}"
        }
      },
      {
        "name": "Manager approval",
        "type": "gated",
        "gate": {
          "message": "Approve expense of ${{input.amount}} for {{input.description}}?",
          "recipients": ["manager@example.com"],
          "timeout": "4h",
          "on_timeout": "cancel"
        }
      },
      {
        "name": "Process payment",
        "type": "http_call",
        "url": "https://api.example.com/payments",
        "method": "POST",
        "body": {
          "expense_id": "{{steps.0.response.id}}"
        },
        "condition": "{{steps.1.status}} == '\''confirmed'\''"
      }
    ],
    "input": {
      "amount": 150.00,
      "description": "Team lunch"
    }
  }'

---

List Chains

GET /chains

Query Parameters

Parameter	Type	Default	Description
status	string	--	Filter by status: pending, running, completed, failed, cancelled
per_page	integer	15	Results per page (max 100)
page	integer	1	Page number

Response

{
  "data": [
    {
      "id": "01chain789-...",
      "name": "Expense Approval Workflow",
      "status": "running",
      "current_step": 1,
      "created_at": "2026-01-15T10:00:00Z"
    }
  ],
  "meta": {
    "current_page": 1,
    "last_page": 1,
    "total": 1
  }
}

---

Get Chain

GET /chains/{id}

Returns the chain with its full step array, including each step's current status, response data (in context), started_at, and completed_at timestamps.

Response

{
  "data": {
    "id": "01chain789-...",
    "name": "Expense Approval Workflow",
    "status": "running",
    "current_step": 1,
    "steps": [
      {
        "name": "Submit expense",
        "type": "http_call",
        "status": "completed",
        "started_at": "2026-01-15T10:00:05Z",
        "completed_at": "2026-01-15T10:00:06Z"
      },
      {
        "name": "Manager approval",
        "type": "approval",
        "status": "running",
        "started_at": "2026-01-15T10:00:07Z",
        "completed_at": null
      },
      {
        "name": "Process payment",
        "type": "http_call",
        "status": "pending",
        "started_at": null,
        "completed_at": null
      }
    ],
    "context": {
      "steps": {
        "0": { "status": "completed", "response": { "id": "exp_123" } }
      }
    },
    "error_handling": "fail_chain",
    "created_at": "2026-01-15T10:00:00Z"
  }
}

---

Cancel Chain

DELETE /chains/{id}

Only chains in pending or running status can be cancelled. Cancelling a chain also cancels any currently pending steps.

Response

{
  "data": {
    "id": "01chain789-...",
    "status": "cancelled"
  }
}

---

Statuses

Chain statuses: pending, running, completed, failed, cancelled

Step statuses: pending, running, completed, failed, skipped, cancelled