Agent Skills · JSON Structure

Agent Skills Tool Result Structure

The output returned to an AI agent after executing a tool skill.

Type: object Properties: 4 Required: 3

Agent SkillsAI AgentsTool UseFunction CallingMCPAgentic AIAutomation

ToolResult is a JSON Structure definition published by Agent Skills, describing 4 properties, of which 3 are required. It conforms to the https://json-structure.org/meta/core/v0/# meta-schema.

Properties

type tool_use_id content is_error

Meta-schema: https://json-structure.org/meta/core/v0/#

JSON Structure

{
  "$schema": "https://json-structure.org/meta/core/v0/#",
  "$id": "https://raw.githubusercontent.com/api-evangelist/agent-skills/refs/heads/main/json-structure/agent-skills-tool-result-structure.json",
  "name": "ToolResult",
  "description": "The output returned to an AI agent after executing a tool skill.",
  "type": "object",
  "properties": {
    "type": {
      "type": "string",
      "description": "Content block type, always tool_result.",
      "example": "tool_result"
    },
    "tool_use_id": {
      "type": "string",
      "description": "The id of the tool_use block this result corresponds to.",
      "example": "toolu_01A09q90qw90lq917835lq9"
    },
    "content": {
      "description": "The result content returned from the tool. Can be a string or array of content blocks.",
      "oneOf": [
        {
          "type": "string"
        },
        {
          "type": "array",
          "items": {
            "type": "object",
            "properties": {
              "type": {
                "type": "string"
              },
              "text": {
                "type": "string"
              }
            }
          }
        }
      ],
      "example": "72\u00b0F and sunny in San Francisco, CA"
    },
    "is_error": {
      "type": "boolean",
      "description": "When true, indicates the tool execution returned an error.",
      "example": false
    }
  },
  "required": [
    "type",
    "tool_use_id",
    "content"
  ]
}