LangChain.MCP.SchemaConverter (LangChain MCP v0.2.0)

Converts MCP tool input schemas (JSON Schema format) to LangChain FunctionParam structures.

MCP tools define their parameters using JSON Schema format. This module handles the conversion to LangChain's FunctionParam format, supporting:

Simple types (string, integer, number, boolean)
Arrays (with item types)
Objects (with nested properties)
Enums
Required fields
Descriptions

Examples

# Simple parameter
schema = %{
  "type" => "object",
  "properties" => %{
    "query" => %{"type" => "string", "description" => "Search query"}
  },
  "required" => ["query"]
}

params = SchemaConverter.to_parameters(schema)
# => [%FunctionParam{name: "query", type: :string, description: "Search query", required: true}]

# Complex nested object
schema = %{
  "type" => "object",
  "properties" => %{
    "user" => %{
      "type" => "object",
      "properties" => %{
        "name" => %{"type" => "string"},
        "age" => %{"type" => "integer"}
      },
      "required" => ["name"]
    }
  }
}

params = SchemaConverter.to_parameters(schema)

Summary

Types

json_schema()

Functions

convert_property(name, prop_schema, required \\ false)

Converts a single property from JSON Schema to FunctionParam.

from_parameters(params)

Converts LangChain FunctionParam list back to JSON Schema format.

to_parameters(schema)

Converts a JSON Schema object to a list of LangChain FunctionParam structs.

Types

json_schema()

@type json_schema() :: map()

Functions

convert_property(name, prop_schema, required \\ false)

@spec convert_property(String.t(), map(), boolean()) ::
  LangChain.FunctionParam.t() | nil

Converts a single property from JSON Schema to FunctionParam.

Parameters

name - Property name
prop_schema - Property schema map
required - Whether this property is required

Returns

FunctionParam.t() or nil if conversion fails

from_parameters(params)

@spec from_parameters([LangChain.FunctionParam.t()]) :: json_schema()

Converts LangChain FunctionParam list back to JSON Schema format.

This is useful for debugging or when you need to reconstruct the original schema.

Parameters

params - List of FunctionParam structs

Returns

JSON Schema map

Examples

iex> params = [
...>   FunctionParam.new!(%{name: "query", type: :string, required: true})
...> ]
iex> schema = SchemaConverter.from_parameters(params)
iex> schema["type"]
"object"
iex> schema["required"]
["query"]

to_parameters(schema)

@spec to_parameters(json_schema()) :: [LangChain.FunctionParam.t()]

Converts a JSON Schema object to a list of LangChain FunctionParam structs.

The schema should be an object with type: "object", properties, and optionally required.

Parameters

schema - JSON Schema map (typically from MCP tool's inputSchema)

Returns

List of FunctionParam structs

Examples

iex> schema = %{
...>   "type" => "object",
...>   "properties" => %{
...>     "name" => %{"type" => "string"},
...>     "count" => %{"type" => "integer"}
...>   },
...>   "required" => ["name"]
...> }
iex> params = SchemaConverter.to_parameters(schema)
iex> length(params)
2
iex> Enum.find(params, & &1.name == "name").required
true