dify/api/controllers/API_SCHEMA_GUIDE.md

API Schema Guide

This guide describes the expected Flask-RESTX + Pydantic pattern for controller request payloads, query parameters, response schemas, and Swagger documentation.

Principles

• Use Pydantic BaseModel for request bodies and query parameters.
• Use fields.base.ResponseModel for response DTOs.
• Keep runtime validation and Swagger documentation wired to the same Pydantic model.
• Prefer explicit validation and serialization in controller methods over Flask-RESTX marshalling.
• Do not add new Flask-RESTX fields.* dictionaries, Namespace.model(...) exports, or @marshal_with(...) for migrated or new endpoints.
• Do not use @ns.expect(...) for GET query parameters. Flask-RESTX documents that as a request body.

Naming

• Request body models: use a Payload suffix.
  • Example: WorkflowRunPayload, DatasourceVariablesPayload.
• Query parameter models: use a Query suffix.
  • Example: WorkflowRunListQuery, MessageListQuery.
• Response models: use a Response suffix and inherit from ResponseModel.
  • Example: WorkflowRunDetailResponse, WorkflowRunNodeExecutionListResponse.
• Use ListResponse or PaginationResponse for wrapper responses.
  • Example: WorkflowRunNodeExecutionListResponse, WorkflowRunPaginationResponse.
• Keep these models near the controller when they are endpoint-specific. Move them to fields/*_fields.py only when shared by multiple controllers.

Registering Models For Swagger

Use helpers from controllers.common.schema.

from controllers.common.schema import (
    query_params_from_model,
    register_response_schema_models,
    register_schema_models,
)

Register request payload and query models with register_schema_models(...):

register_schema_models(
    console_ns,
    WorkflowRunPayload,
    WorkflowRunListQuery,
)

Register response models with register_response_schema_models(...):

register_response_schema_models(
    console_ns,
    WorkflowRunDetailResponse,
    WorkflowRunPaginationResponse,
)

Response models are registered in Pydantic serialization mode. This matters when a response model uses validation_alias to read internal object attributes but emits public API field names. For example, a response model can validate from inputs_dict while documenting and serializing inputs.

Request Bodies

For non-GET request bodies:

1. Define a Pydantic Payload model.
2. Register it with register_schema_models(...).
3. Use @ns.expect(ns.models[Payload.__name__]) for Swagger documentation.
4. Validate from ns.payload or {} inside the controller.

class DraftWorkflowNodeRunPayload(BaseModel):
    inputs: dict[str, Any]
    query: str = ""


register_schema_models(console_ns, DraftWorkflowNodeRunPayload)


@console_ns.expect(console_ns.models[DraftWorkflowNodeRunPayload.__name__])
def post(self, app_model: App, node_id: str):
    payload = DraftWorkflowNodeRunPayload.model_validate(console_ns.payload or {})
    result = service.run(..., inputs=payload.inputs, query=payload.query)
    return WorkflowRunNodeExecutionResponse.model_validate(result, from_attributes=True).model_dump(mode="json")

Query Parameters

For GET query parameters:

1. Define a Pydantic Query model.
2. Register it with register_schema_models(...) if it is referenced elsewhere in docs, or only use query_params_from_model(...) if a body schema is not needed.
3. Use @ns.doc(params=query_params_from_model(QueryModel)).
4. Validate from request.args.to_dict(flat=True) or an explicit dict when type coercion is needed.

class WorkflowRunListQuery(BaseModel):
    last_id: str | None = Field(default=None, description="Last run ID for pagination")
    limit: int = Field(default=20, ge=1, le=100, description="Number of items per page (1-100)")


@console_ns.doc(params=query_params_from_model(WorkflowRunListQuery))
def get(self, app_model: App):
    query = WorkflowRunListQuery.model_validate(request.args.to_dict(flat=True))
    result = service.list(..., limit=query.limit, last_id=query.last_id)
    return WorkflowRunPaginationResponse.model_validate(result, from_attributes=True).model_dump(mode="json")

Do not do this for GET query parameters:

@console_ns.expect(console_ns.models[WorkflowRunListQuery.__name__])
def get(...):
    ...

That documents a GET request body and is not the expected contract.

Responses

Response models should inherit from ResponseModel:

class WorkflowRunNodeExecutionResponse(ResponseModel):
    id: str
    inputs: Any = Field(default=None, validation_alias="inputs_dict")
    process_data: Any = Field(default=None, validation_alias="process_data_dict")
    outputs: Any = Field(default=None, validation_alias="outputs_dict")

Document response models with @ns.response(...):

@console_ns.response(
    200,
    "Node run started successfully",
    console_ns.models[WorkflowRunNodeExecutionResponse.__name__],
)
def post(...):
    ...

Serialize explicitly:

return WorkflowRunNodeExecutionResponse.model_validate(
    workflow_node_execution,
    from_attributes=True,
).model_dump(mode="json")

If the service can return None, translate that into the expected HTTP error before validation:

workflow_run = service.get_workflow_run(...)
if workflow_run is None:
    raise NotFound("Workflow run not found")

return WorkflowRunDetailResponse.model_validate(workflow_run, from_attributes=True).model_dump(mode="json")

Legacy Flask-RESTX Patterns

Avoid adding these patterns to new or migrated endpoints:

• ns.model(...) for new request/response DTOs.
• Module-level exported RESTX model objects such as workflow_run_detail_model.
• fields.Nested({...}) with raw inline dict field maps.
• @marshal_with(...) for response serialization.
• @ns.expect(...) for GET query params.

Existing legacy field dictionaries may remain where an endpoint has not yet been migrated. Keep that compatibility local to the legacy area and avoid importing RESTX model objects from controllers.

Verifying Swagger

For schema and documentation changes, run focused tests and generate Swagger JSON:

uv run --project . pytest tests/unit_tests/controllers/common/test_schema.py
uv run --project . pytest tests/unit_tests/commands/test_generate_swagger_specs.py tests/unit_tests/controllers/test_swagger.py
uv run --project . dev/generate_swagger_specs.py --output-dir /tmp/dify-openapi-check

Inspect affected endpoints with jq. Check that:

• GET parameters are in: query.
• Request bodies appear only where the endpoint has a body.
• Responses reference the expected *Response schema.
• Response schemas use public serialized names, not internal validation aliases like inputs_dict.