---
title: openapi
sidebarTitle: openapi
---

# `fastmcp.utilities.openapi`

## Functions

### `format_array_parameter` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/utilities/openapi.py#L41" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
format_array_parameter(values: list, parameter_name: str, is_query_parameter: bool = False) -> str | list
```


Format an array parameter according to OpenAPI specifications.

**Args:**
- `values`: List of values to format
- `parameter_name`: Name of the parameter (for error messages)
- `is_query_parameter`: If True, can return list for explode=True behavior

**Returns:**
- String (comma-separated) or list (for query params with explode=True)


### `format_deep_object_parameter` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/utilities/openapi.py#L95" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
format_deep_object_parameter(param_value: dict, parameter_name: str) -> dict[str, str]
```


Format a dictionary parameter for deepObject style serialization.

According to OpenAPI 3.0 spec, deepObject style with explode=true serializes
object properties as separate query parameters with bracket notation.

For example: `{"id": "123", "type": "user"}` becomes `param[id]=123&param[type]=user`.

**Args:**
- `param_value`: Dictionary value to format
- `parameter_name`: Name of the parameter

**Returns:**
- Dictionary with bracketed parameter names as keys


### `parse_openapi_to_http_routes` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/utilities/openapi.py#L205" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
parse_openapi_to_http_routes(openapi_dict: dict[str, Any]) -> list[HTTPRoute]
```


Parses an OpenAPI schema dictionary into a list of HTTPRoute objects
using the openapi-pydantic library.

Supports both OpenAPI 3.0.x and 3.1.x versions.


### `clean_schema_for_display` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/utilities/openapi.py#L745" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
clean_schema_for_display(schema: JsonSchema | None) -> JsonSchema | None
```


Clean up a schema dictionary for display by removing internal/complex fields.


### `generate_example_from_schema` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/utilities/openapi.py#L805" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
generate_example_from_schema(schema: JsonSchema | None) -> Any
```


Generate a simple example value from a JSON schema dictionary.
Very basic implementation focusing on types.


### `format_json_for_description` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/utilities/openapi.py#L888" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
format_json_for_description(data: Any, indent: int = 2) -> str
```


Formats Python data as a JSON string block for markdown.


### `format_description_with_responses` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/utilities/openapi.py#L897" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
format_description_with_responses(base_description: str, responses: dict[str, Any], parameters: list[ParameterInfo] | None = None, request_body: RequestBodyInfo | None = None) -> str
```


Formats the base description string with response, parameter, and request body information.

**Args:**
- `base_description`: The initial description to be formatted.
- `responses`: A dictionary of response information, keyed by status code.
- `parameters`: A list of parameter information,
including path and query parameters. Each parameter includes details such as name,
location, whether it is required, and a description.
- `request_body`: Information about the request body,
including its description, whether it is required, and its content schema.

**Returns:**
- The formatted description string with additional details about responses, parameters,
- and the request body.


### `extract_output_schema_from_responses` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/utilities/openapi.py#L1423" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
extract_output_schema_from_responses(responses: dict[str, ResponseInfo], schema_definitions: dict[str, Any] | None = None, openapi_version: str | None = None) -> dict[str, Any] | None
```


Extract output schema from OpenAPI responses for use as MCP tool output schema.

This function finds the first successful response (200, 201, 202, 204) with a
JSON-compatible content type and extracts its schema. If the schema is not an
object type, it wraps it to comply with MCP requirements.

**Args:**
- `responses`: Dictionary of ResponseInfo objects keyed by status code
- `schema_definitions`: Optional schema definitions to include in the output schema
- `openapi_version`: OpenAPI version string, used to optimize nullable field handling

**Returns:**
- MCP-compliant output schema with potential wrapping, or None if no suitable schema found


## Classes

### `ParameterInfo` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/utilities/openapi.py#L128" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>


Represents a single parameter for an HTTP operation in our IR.


### `RequestBodyInfo` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/utilities/openapi.py#L140" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>


Represents the request body for an HTTP operation in our IR.


### `ResponseInfo` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/utilities/openapi.py#L150" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>


Represents response information in our IR.


### `HTTPRoute` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/utilities/openapi.py#L158" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>


Intermediate Representation for a single OpenAPI operation.


### `OpenAPIParser` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/utilities/openapi.py#L259" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>


Unified parser for OpenAPI schemas with generic type parameters to handle both 3.0 and 3.1.


**Methods:**

#### `parse` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/utilities/openapi.py#L623" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
parse(self) -> list[HTTPRoute]
```

Parse the OpenAPI schema into HTTP routes.

