{
  "openapi": "3.1.0",
  "info": {
    "title": "Open eXecution Protocol (OXP) Standard",
    "version": "1.0.0",
    "description": "A standard for calling tools (functions or services) in a distributed system.",
    "license": {
      "name": "MIT",
      "url": "https://opensource.org/licenses/MIT"
    },
    "contact": {
      "url": "https://openexecprotocol.org"
    }
  },
  "paths": {
    "/health": {
      "get": {
        "operationId": "health-check",
        "summary": "Check health",
        "description": "Checks the health status of the server.",
        "security": [{}],
        "responses": {
          "200": {
            "description": "Server is healthy."
          },
          "503": {
            "description": "Server is unhealthy and cannot accept requests."
          }
        }
      }
    },
    "/tools": {
      "get": {
        "operationId": "list-tools",
        "summary": "List tools",
        "description": "Returns a list of tool definitions.",
        "security": [
          {
            "bearerAuth": []
          },
          {}
        ],
        "requestBody": {
          "required": false,
          "content": {
            "application/json": {
              "schema": {
                "properties": {
                  "$schema": {
                    "type": "string",
                    "format": "uri"
                  }
                }
              }
            }
          }
        },
        "responses": {
          "200": {
            "description": "A list of available tools.",
            "content": {
              "application/json": {
                "schema": {
                  "properties": {
                    "$schema": {
                      "type": "string",
                      "format": "uri"
                    },
                    "items": {
                      "type": "array",
                      "items": {
                        "$ref": "#/components/schemas/ToolDefinition"
                      }
                    }
                  },
                  "required": ["items"]
                }
              }
            }
          },
          "401": {
            "description": "Unauthorized. The request requires authentication, but the provided credentials are invalid or missing."
          }
        }
      }
    },
    "/tools/call": {
      "post": {
        "operationId": "call-tool",
        "summary": "Call tool",
        "description": "Calls a tool with the given parameters.",
        "security": [
          {
            "bearerAuth": []
          },
          {}
        ],
        "requestBody": {
          "required": true,
          "content": {
            "application/json": {
              "schema": {
                "properties": {
                  "$schema": {
                    "type": "string",
                    "format": "uri"
                  },
                  "request": {
                    "$ref": "#/components/schemas/CallToolRequest"
                  }
                },
                "required": ["request"]
              }
            }
          }
        },
        "responses": {
          "200": {
            "description": "Response from tool.",
            "content": {
              "application/json": {
                "schema": {
                  "properties": {
                    "$schema": {
                      "type": "string",
                      "format": "uri"
                    },
                    "result": {
                      "$ref": "#/components/schemas/CallToolResponse"
                    }
                  },
                  "required": ["result"]
                }
              }
            }
          },
          "400": {
            "description": "The request is invalid or could not be processed.",
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/ServerErrorResponse"
                }
              }
            }
          },
          "401": {
            "description": "Unauthorized. The request requires authentication, but the provided credentials are invalid or missing."
          },
          "422": {
            "description": "The tool call is valid, but the parameters are invalid (missing, incorrect type, etc).",
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/ValidationErrorResponse"
                }
              }
            }
          }
        }
      }
    }
  },
  "components": {
    "securitySchemes": {
      "bearerAuth": {
        "type": "http",
        "scheme": "bearer",
        "bearerFormat": "JWT"
      }
    },
    "schemas": {
      "ToolId": {
        "type": "string",
        "description": "A tool's unique identifier in the format 'Toolkit.Tool[@version]', where @version is optional.",
        "pattern": "^[A-Za-z0-9_]+\\.[A-Za-z0-9_]+(@([0-9]+|[0-9]+\\.[0-9]+\\.[0-9]+))?$",
        "example": [
          "Calculator.Add",
          "Calculator.Add@1",
          "Calculator.Add@1.0.0"
        ]
      },
      "ToolVersion": {
        "type": "string",
        "description": "A tool's semantic version in the format 'x.y.z', where x, y, and z are integers.",
        "pattern": "^[0-9]+\\.[0-9]+\\.[0-9]+$",
        "example": "1.2.3"
      },
      "ToolSecret": {
        "type": "object",
        "properties": {
          "id": {
            "type": "string",
            "description": "The secret's unique identifier."
          },
          "value": {
            "type": "string",
            "description": "The secret's value."
          }
        },
        "required": ["id", "value"],
        "additionalProperties": true
      },
      "ToolDefinition": {
        "type": "object",
        "properties": {
          "id": {
            "$ref": "#/components/schemas/ToolId"
          },
          "name": {
            "type": "string",
            "description": "The tool's name. Only allows alphanumeric characters, underscores, and dashes.",
            "pattern": "^[A-Za-z0-9_-]{1,64}$",
            "example": ["Calculator_Add", "Email_GetEmails"]
          },
          "description": {
            "type": "string",
            "description": "A plain language explanation of when and how the tool should be used."
          },
          "version": {
            "$ref": "#/components/schemas/ToolVersion"
          },
          "input_schema": {
            "type": "object",
            "additionalProperties": true,
            "description": "JSON Schema describing the input parameters for the tool. Supports standard JSON Schema validation but excludes $ref and definitions/schemas for simplicity."
          },
          "output_schema": {
            "oneOf": [
              {
                "type": "object",
                "additionalProperties": true,
                "description": "JSON Schema describing the output parameters for the tool. Supports standard JSON Schema validation but excludes $ref and definitions/schemas for simplicity."
              },
              {
                "type": "null",
                "description": "Null indicates the tool does not return any value."
              }
            ],
            "description": "Schema describing the output of the tool. Can be a JSON Schema object or null if the tool doesn't return a value."
          },
          "requirements": {
            "type": "object",
            "properties": {
              "authorization": {
                "type": "array",
                "items": {
                  "type": "object",
                  "properties": {
                    "id": {
                      "type": "string",
                      "description": "A provider's unique identifier, allowing the tool to specify a specific authorization provider."
                    },
                    "oauth2": {
                      "type": "object",
                      "description": "OAuth 2.0-specific authorization details.",
                      "properties": {
                        "scopes": {
                          "type": "array",
                          "items": {
                            "type": "string"
                          }
                        }
                      },
                      "additionalProperties": true
                    }
                  }
                },
                "required": ["id"],
                "additionalProperties": true
              },
              "secrets": {
                "type": "array",
                "items": {
                  "type": "object",
                  "properties": {
                    "id": {
                      "type": "string",
                      "description": "The secret's unique identifier."
                    }
                  },
                  "required": ["id"],
                  "additionalProperties": true
                }
              },
              "user_id": {
                "type": "boolean",
                "description": "Whether the tool requires a user ID."
              }
            },
            "additionalProperties": true
          }
        },
        "required": ["id", "name", "description", "version"],
        "additionalProperties": false
      },
      "CallToolRequest": {
        "type": "object",
        "properties": {
          "call_id": {
            "type": "string",
            "description": "A unique identifier (e.g. UUID) for this tool call. Used as an idempotency key. If omitted, the server will generate an ID."
          },
          "trace_id": {
            "type": "string",
            "description": "An optional trace identifier for the tool call."
          },
          "tool_id": {
            "$ref": "#/components/schemas/ToolId"
          },
          "input": {
            "type": "object",
            "description": "The input parameters for the tool call.",
            "additionalProperties": true
          },
          "context": {
            "type": "object",
            "properties": {
              "authorization": {
                "type": "array",
                "description": "The authorization information for the tool call.",
                "items": {
                  "type": "object",
                  "properties": {
                    "id": {
                      "type": "string",
                      "description": "The unique identifier for the authorization method or authorization provider."
                    },
                    "token": {
                      "type": "string",
                      "description": "The token for the tool call."
                    }
                  },
                  "required": ["id", "token"],
                  "additionalProperties": true
                }
              },
              "secrets": {
                "type": "array",
                "description": "The secrets for the tool call.",
                "items": {
                  "$ref": "#/components/schemas/ToolSecret"
                },
                "additionalProperties": true
              },
              "user_id": {
                "type": "string",
                "description": "A unique ID that identifies the user, if required by the tool."
              }
            },
            "additionalProperties": true
          }
        },
        "required": ["tool_id"],
        "additionalProperties": false
      },
      "CallToolResponse": {
        "type": "object",
        "properties": {
          "call_id": {
            "type": "string",
            "description": "The unique identifier (e.g. UUID) for this tool call. If an ID is not provided by the client, the server will generate one."
          },
          "duration": {
            "type": "number",
            "description": "The runtime duration of the tool call, in milliseconds"
          },
          "success": {
            "type": "boolean",
            "description": "Whether the tool call was successful. If the `error` field is present, this field will be false."
          }
        },
        "required": ["call_id", "success"],
        "oneOf": [
          {
            "properties": {
              "success": { "enum": [true] },
              "value": {
                "type": [
                  "object",
                  "array",
                  "string",
                  "number",
                  "boolean",
                  "null"
                ],
                "additionalProperties": true,
                "description": "The value returned from the tool."
              }
            },
            "not": { "required": ["error"] }
          },
          {
            "properties": {
              "success": { "enum": [false] },
              "error": {
                "$ref": "#/components/schemas/ToolError"
              }
            },
            "required": ["error"],
            "not": { "required": ["value"] }
          }
        ],
        "additionalProperties": false
      },
      "ServerErrorResponse": {
        "type": "object",
        "properties": {
          "$schema": {
            "type": "string",
            "format": "uri"
          },
          "message": {
            "type": "string",
            "description": "The error message."
          },
          "developer_message": {
            "type": "string",
            "description": "An internal message that will be logged but will not be shown to the user or the AI model"
          },
          "missing_requirements": {
            "type": "object",
            "description": "A map of missing requirements.",
            "properties": {
              "authorization": {
                "type": "array",
                "description": "A list of authorization challenges that must be completed before the tool can be called.",
                "items": {
                  "$ref": "#/components/schemas/ToolAuthorizationChallenge"
                }
              },
              "user_id": {
                "type": "boolean",
                "description": "Whether the tool requires a user ID."
              }
            }
          }
        },
        "required": ["message"],
        "additionalProperties": true
      },
      "ValidationErrorResponse": {
        "type": "object",
        "properties": {
          "$schema": {
            "type": "string",
            "format": "uri"
          },
          "message": {
            "type": "string",
            "description": "The error message."
          },
          "parameter_errors": {
            "type": "object",
            "description": "A map of parameter names to error messages, if parameter-level errors are present."
          }
        },
        "required": ["message"],
        "additionalProperties": true
      },
      "ToolAuthorizationChallenge": {
        "type": "object",
        "properties": {
          "id": {
            "type": "string",
            "description": "The unique identifier for the authorization challenge."
          },
          "url": {
            "type": "string",
            "description": "The URL the user must visit to complete the authorization challenge."
          },
          "check_url": {
            "type": "string",
            "description": "The URL to check the status of the authorization challenge."
          }
        },
        "required": ["id", "url"],
        "additionalProperties": false
      },
      "ToolError": {
        "type": "object",
        "description": "An error that occurred inside the tool function.",
        "properties": {
          "message": {
            "type": "string",
            "description": "An error message that can be shown to the user or the AI model."
          },
          "developer_message": {
            "type": "string",
            "description": "An internal message that will be logged but will not be shown to the user or the AI model."
          },
          "can_retry": {
            "type": "boolean",
            "description": "Whether the tool call can be retried by the client.",
            "default": false
          },
          "additional_prompt_content": {
            "type": "string",
            "description": "Additional content to be included in the retry prompt."
          },
          "retry_after_ms": {
            "type": "integer",
            "description": "The number of milliseconds (if any) to wait before retrying the tool call."
          }
        },
        "required": ["message"],
        "additionalProperties": true
      }
    }
  }
}