---
title: openapi
sidebarTitle: openapi
---
# `fastmcp.utilities.openapi`
## Functions
### `format_array_parameter`
```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`
```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¶m[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`
```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`
```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`
```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`
```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`
```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`
```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`
Represents a single parameter for an HTTP operation in our IR.
### `RequestBodyInfo`
Represents the request body for an HTTP operation in our IR.
### `ResponseInfo`
Represents response information in our IR.
### `HTTPRoute`
Intermediate Representation for a single OpenAPI operation.
### `OpenAPIParser`
Unified parser for OpenAPI schemas with generic type parameters to handle both 3.0 and 3.1.
**Methods:**
#### `parse`
```python
parse(self) -> list[HTTPRoute]
```
Parse the OpenAPI schema into HTTP routes.