## 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
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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:
JsonSchemaAdditionalPropertiesToolDefinitionToolSpecConfiguredToolSpecResponsesApiToolFreeformToolFreeformToolFormatToolSearchOutputToolResponsesApiWebSearchFiltersResponsesApiWebSearchUserLocationResponsesApiNamespaceResponsesApiNamespaceTool- code-mode
ToolSpecadapters andexec/waitspec builders - JS REPL spec builders
- MCP resource,
list_dir, andtest_sync_toolspec builders - local host tool spec builders for shell/exec/request-permissions/view-image
- collaboration and agent-job
ToolSpecbuilders 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-coreorchestration 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:
- Move low-coupling tool primitives here.
- Switch non-core consumers to depend on
codex-toolsdirectly. - Leave compatibility-sensitive adapters in
codex-corewhile downstream call sites are updated. - 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.rsshould remain exports-only.- Business logic should live in named module files such as
foo.rs. - Unit tests for
foo.rsshould live in a siblingfoo_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.