Files
codex/codex-rs/tools/README.md
Michael Bolin caee620a53 codex-tools: introduce named tool definitions (#15953)
## Why

This continues the `codex-tools` migration by moving one more piece of
generic tool-definition bookkeeping out of `codex-core`.

The earlier extraction steps moved shared schema parsing into
`codex-tools`, but `core/src/tools/spec.rs` still had to supply tool
names separately and perform ad hoc rewrites for deferred MCP aliases.
That meant the crate boundary was still awkward: the parsed shape coming
back from `codex-tools` was missing part of the definition that
`codex-core` ultimately needs to assemble a `ResponsesApiTool`.

This change introduces a named `ToolDefinition` in `codex-tools` so both
MCP tools and dynamic tools cross the crate boundary in the same
reusable model. `codex-core` still owns the final `ResponsesApiTool`
assembly, but less of the generic tool-definition shaping logic stays
behind in `core`.

## What changed

- replaced `ParsedToolDefinition` with a named `ToolDefinition` in
`codex-rs/tools/src/tool_definition.rs`
- added `codex-rs/tools/src/tool_definition_tests.rs` for `renamed()`
and `into_deferred()`
- updated `parse_dynamic_tool()` and `parse_mcp_tool()` to return
`ToolDefinition`
- simplified `codex-rs/core/src/tools/spec.rs` so it adapts
`ToolDefinition` into `ResponsesApiTool` instead of rewriting names and
deferred fields inline
- updated parser tests and `codex-rs/tools/README.md` to reflect the
named tool-definition model

## Test plan

- `cargo test -p codex-tools`
- `cargo test -p codex-core --lib tools::spec::`
2026-03-27 12:02:55 -07:00

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Markdown

# codex-tools
`codex-tools` is intended to become the home for tool-related code that is
shared across multiple crates and does not need to stay coupled to
`codex-core`.
Today this crate is intentionally small. It currently owns the shared tool
schema primitives that no longer need to live in `core/src/tools/spec.rs`:
- `JsonSchema`
- `AdditionalProperties`
- `ToolDefinition`
- `parse_tool_input_schema()`
- `parse_dynamic_tool()`
- `parse_mcp_tool()`
- `mcp_call_tool_result_output_schema()`
That extraction is the first step in a longer migration. The goal is not to
move all of `core/src/tools` into this crate in one shot. Instead, the plan is
to peel off reusable pieces in reviewable increments while keeping
compatibility-sensitive orchestration in `codex-core` until the surrounding
boundaries are ready.
## Vision
Over time, this crate should hold tool-facing primitives that are shared by
multiple consumers, for example:
- schema and spec data models
- tool input/output parsing helpers
- tool metadata and compatibility shims that do not depend on `codex-core`
- other narrowly scoped utility code that multiple crates need
The corresponding non-goals are just as important:
- do not move `codex-core` orchestration here prematurely
- do not pull `Session` / `TurnContext` / approval flow / runtime execution
logic into this crate unless those dependencies have first been split into
stable shared interfaces
- do not turn this crate into a grab-bag for unrelated helper code
## Migration approach
The expected migration shape is:
1. Move low-coupling tool primitives here.
2. Switch non-core consumers to depend on `codex-tools` directly.
3. Leave compatibility-sensitive adapters in `codex-core` while downstream
call sites are updated.
4. Only extract higher-level tool infrastructure after the crate boundaries are
clear and independently testable.
That means it is normal for `codex-core` to temporarily re-export types or
helpers from `codex-tools` during the transition.
## Crate conventions
This crate should start with stricter structure than `core/src/tools` so it
stays easy to grow:
- `src/lib.rs` should remain exports-only.
- Business logic should live in named module files such as `foo.rs`.
- Unit tests for `foo.rs` should live in a sibling `foo_tests.rs`.
- The implementation file should wire tests with:
```rust
#[cfg(test)]
#[path = "foo_tests.rs"]
mod tests;
```
If this crate starts accumulating code that needs runtime state from
`codex-core`, that is a sign to revisit the extraction boundary before adding
more here.