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Twilio

by io.github.pipeworx-io
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Twilio Send Sms

twilio_send_sms
Idempotent

Send an SMS message via Twilio. Returns the message SID and status.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
toYesDestination phone number in E.164 format (e.g., +15551234567)
bodyYesMessage body text (max 1600 characters)
fromYesTwilio phone number to send from in E.164 format
_authTokenYesTwilio Auth Token
_accountSidYesTwilio Account SID (starts with AC...)

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
toNoDestination phone number
sidNoMessage SID (unique identifier)
bodyNoMessage body text
fromNoSender phone number
priceNoCost of the message
statusNoMessage status (queued, sending, sent, failed, etc.)
date_sentNoISO 8601 timestamp when sent
error_codeNoError code if failed
price_unitNoCurrency unit (USD)
account_sidNoAccount SID
date_createdNoISO 8601 timestamp of creation
date_updatedNoISO 8601 timestamp of last update
error_messageNoError message if failed

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changed
    • changedOutput schema / (root)
      Previous value: -nullNew value: +{
+  "properties": {
+    "account_sid": {
+      "description": "Account SID",
+      "type": "string"
+    },
+    "body": {
+      "description": "Message body text",
+      "type": "string"
+    },
+    "date_created": {
+      "description": "ISO 8601 timestamp of creation",
+      "type": "string"
+    },
+    "date_sent": {
+      "description": "ISO 8601 timestamp when sent",
+      "type": "string"
+    },
+    "date_updated": {
+      "description": "ISO 8601 timestamp of last update",
+      "type": "string"
+    },
+    "error_code": {
+      "description": "Error code if failed",
+      "type": [
+        "integer",
+        "null"
+      ]
+    },
+    "error_message": {
+      "description": "Error message if failed",
+      "type": [
+        "string",
+        "null"
+      ]
+    },
+    "from": {
+      "description": "Sender phone number",
+      "type": "string"
+    },
+    "price": {
+      "description": "Cost of the message",
+      "type": [
+        "string",
+        "null"
+      ]
+    },
+    "price_unit": {
+      "description": "Currency unit (USD)",
+      "type": "string"
+    },
+    "sid": {
+      "description": "Message SID (unique identifier)",
+      "type": "string"
+    },
+    "status": {
+      "description": "Message status (queued, sending, sent, failed, etc.)",
+      "type": "string"
+    },
+    "to": {
+      "description": "Destination phone number",
+      "type": "string"
+    }
+  },
+  "type": "object"
+}
  2. Changed1 schema field changed
    • addedInput schema / examples
      Added value: +[
+  {
+    "_accountSid": "ACxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
+    "_authToken": "your-twilio-auth-token",
+    "body": "Hello! This is a test message from Twilio.",
+    "from": "+15559876543",
+    "to": "+15551234567"
+  },
+  {
+    "_accountSid": "ACxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
+    "_authToken": "your-twilio-auth-token",
+    "body": "Your verification code is: 123456",
+    "from": "+15559876543",
+    "to": "+442071838750"
+  }
+]
  3. First observed

TDQS

A4/5.0
Behavior3/5

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

Annotations already indicate mutation (readOnlyHint=false), idempotency hint (idempotentHint=true), and non-destructive nature. The description adds the return value (SID and status), which is useful but does not address rate limits, costs, or clarification of idempotency. Thus, it provides some value beyond annotations.

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 a single sentence of 10 words, front-loading the main purpose and return value. Every word is necessary; no waste.

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?

The description adequately covers the main purpose and return format. With an output schema available (as per context signals), it complements the schema well. It could mention character limits or authentication requirements, but the schema already covers those.

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%, so the schema already documents all parameters with descriptions. The tool description does not add new semantic meaning about the parameters beyond what is already in the schema.

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 'Send an SMS message via Twilio' and the return value 'Returns the message SID and status.' This distinguishes it from sibling tools like twilio_get_message or twilio_list_messages, which are for reading or listing messages.

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 tool's purpose is clear enough that an agent would know when to use it (sending SMS) versus alternatives (retrieving messages or making calls). However, there is no explicit guidance on when not to use it or mention of 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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