Files
langchain/libs
Sydney Runkle dc7a009371 feat(core): introduce ToolSchema as root schema cache; replace TypedDict conversion with TypeAdapter (#37103)
Builds on #37101.

---

Two changes in one commit, both motivated by the same principle: a
single, clean owner for everything schema-related on a tool.

## `ToolSchema` — the root cache

Previously `BaseTool` had three independent `cached_property` slots
(`tool_call_schema`, `args`, `_approximate_schema_chars`) that all
computed overlapping data and each needed individual invalidation. This
PR replaces them with a single `ToolSchema` dataclass and one
`tool_schema` cached property that is the sole root:

```python
@dataclass
class ToolSchema:
    name: str
    description: str
    validator: TypeAdapter      # validates tool call inputs
    json_schema: dict           # sent to LLMs
    pydantic_schema: Any        # model class or dict (backward compat)
    args: dict                  # properties from json_schema
    approximate_chars: int      # precomputed for token estimation
```

`BaseTool.tool_call_schema`, `BaseTool.args`, and
`BaseTool._approximate_schema_chars` are now plain `@property` delegates
to `tool_schema`. `__setattr__` only needs to pop one key on mutation
instead of four. The `is`-identity caching tests still pass because all
delegates read from the same cached `ToolSchema` object.

`ToolSchema` is exported from `langchain_core.tools` and can be used
directly by integrations that want to consume both the validator and the
schema without going through `BaseTool`.

## `TypeAdapter`-based TypedDict conversion

`_convert_any_typed_dicts_to_pydantic` was a ~70-line recursive function
that converted TypedDicts to throwaway pydantic v1 model classes just to
call `.schema()`. Replaced with:

```python
adapter = TypeAdapter(typed_dict)
schema = adapter.json_schema()
```

Pydantic v2's `TypeAdapter` handles everything the old code did — nested
TypedDicts, generic containers, `Annotated` metadata — and also
correctly handles `NotRequired` and `Required` annotations, which the v1
path did not. A new test `test__convert_typed_dict_not_required`
verifies this:

```python
class Tool(TypedDict):
    required_field: str
    optional_field: NotRequired[int]

result = _convert_typed_dict_to_openai_function(Tool)
assert "required_field" in result["parameters"]["required"]
assert "optional_field" not in result["parameters"]["required"]
```

Field descriptions from Google-style docstrings and `Annotated[T, ...,
"description"]` metadata are preserved by post-processing the schema
after generation.

The old `test__convert_typed_dict_to_openai_function_fail` test expected
a `TypeError` for `MutableSet` because pydantic v1 didn't support it.
pydantic v2 does; the test is updated to verify successful conversion
instead.

## What stays unchanged

- All public `BaseTool` API signatures — `tool_call_schema`, `args`,
`get_input_schema()` all have the same signatures and return types as
before.
- `pydantic.v1` acceptance for `args_schema` — tools with v1 model
schemas continue to work.

> AI-agent assisted contribution.

---------

Co-authored-by: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>
2026-05-01 09:25:22 -04:00
..

LangChain Monorepo

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Important

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This repository is structured as a monorepo, with various packages located in this libs/ directory. Packages to note in this directory include:

core/             # Core primitives and abstractions for langchain
langchain/        # langchain-classic
langchain_v1/     # langchain
partners/         # Certain third-party providers integrations (see below)
standard-tests/   # Standardized tests for integrations
text-splitters/   # Text splitter utilities

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