Files
codex/codex-rs/tools/README.md
Michael Bolin af568afdd5 codex-tools: extract utility tool specs (#16154)
## Why

The previous `codex-tools` migration steps moved the shared schema
models, local-host specs, collaboration specs, and related adapters out
of `codex-core`, but `core/src/tools/spec.rs` still contained a grab bag
of pure utility tool builders. Those specs do not need session state or
handler logic; they only describe wire shapes for tools that
`codex-core` already knows how to execute.

Moving that remaining low-coupling layer into `codex-tools` keeps the
migration moving in meaningful chunks and trims another large block of
passive tool-spec construction out of `codex-core` without touching the
runtime-coupled handlers.

## What changed

- extended `codex-tools` to own the pure spec builders for:
  - code-mode `exec` / `wait`
  - `js_repl` / `js_repl_reset`
- MCP resource tools `list_mcp_resources`,
`list_mcp_resource_templates`, and `read_mcp_resource`
  - utility tools `list_dir` and `test_sync_tool`
- split those builders across small module files with sibling
`*_tests.rs` coverage, keeping `src/lib.rs` exports-only
- rewired `core/src/tools/spec.rs` to call the extracted builders and
deleted the duplicated core-local implementations
- moved the direct JS REPL grammar seam test out of
`core/src/tools/spec_tests.rs` so it now lives with the extracted
implementation in `codex-tools`
- updated `codex-rs/tools/README.md` so the documented crate boundary
matches the new utility-spec surface

## Test plan

- `CARGO_TARGET_DIR=/tmp/codex-tools-utility-specs cargo test -p
codex-tools`
- `CARGO_TARGET_DIR=/tmp/codex-core-utility-specs cargo test -p
codex-core --lib tools::spec::`
- `just fix -p codex-tools -p codex-core`
- `just argument-comment-lint`

## References

- #15923
- #15928
- #15944
- #15953
- #16031
- #16047
- #16129
- #16132
- #16138
- #16141
2026-03-29 14:34:36 -07:00

3.5 KiB

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 and Responses API tool primitives that no longer need to live in core/src/tools/spec.rs or core/src/client_common.rs:

  • JsonSchema
  • AdditionalProperties
  • ToolDefinition
  • ToolSpec
  • ConfiguredToolSpec
  • ResponsesApiTool
  • FreeformTool
  • FreeformToolFormat
  • ToolSearchOutputTool
  • ResponsesApiWebSearchFilters
  • ResponsesApiWebSearchUserLocation
  • ResponsesApiNamespace
  • ResponsesApiNamespaceTool
  • code-mode ToolSpec adapters and exec / wait spec builders
  • JS REPL spec builders
  • MCP resource, list_dir, and test_sync_tool spec builders
  • local host tool spec builders for shell/exec/request-permissions/view-image
  • collaboration and agent-job ToolSpec builders for spawn/send/wait/close, request_user_input, and CSV fanout/reporting
  • parse_tool_input_schema()
  • parse_dynamic_tool()
  • parse_mcp_tool()
  • create_tools_json_for_responses_api()
  • mcp_call_tool_result_output_schema()
  • tool_definition_to_responses_api_tool()
  • dynamic_tool_to_responses_api_tool()
  • mcp_tool_to_responses_api_tool()
  • mcp_tool_to_deferred_responses_api_tool()
  • augment_tool_spec_for_code_mode()
  • tool_spec_to_code_mode_tool_definition()

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:
#[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.