## Why
This is the next narrow step toward moving concrete tool families out of
core. After #22138 introduced `codex-tool-api`, we still needed a real
end-to-end seam that lets an extension own an executable tool definition
once and have core install it without the temporary `extension-api`
wrapper or a dependency on `codex-tools`.
`codex-tool-api` is the small extension-facing execution contract, while
`codex-tools` still has a different job: host-side shared tool metadata
and planning logic that is not “run this contributed tool”, like spec
shaping, namespaces, discovery, code-mode augmentation, and
MCP/dynamic-to-Responses API conversion
## What changed
- Moved the shared leaf tool-spec and JSON Schema types into
`codex-tool-api`, so the executable contract now lives with
[`ToolBundle`](c538758095/codex-rs/tool-api/src/bundle.rs (L19-L70)).
- Replaced the temporary extension-side tool wrapper with direct
`ToolBundle` use in `codex-extension-api`.
- Taught core to collect contributed bundles, include them in spec
planning, register them through
[`ToolRegistryBuilder::register_tool_bundle`](c538758095/codex-rs/core/src/tools/registry.rs (L653-L667)),
and dispatch them through the existing router/runtime path.
- Added focused coverage for contributed tools becoming model-visible
and dispatchable, plus spec-planning coverage for contributed function
and freeform tools.
## Verification
- Added `extension_tool_bundles_are_model_visible_and_dispatchable` in
`core/src/tools/router_tests.rs`.
- Added spec-plan coverage in `core/src/tools/spec_plan_tests.rs` for
contributed extension bundles.
## Related
- Follow-up to #22138
## Summary
- make the shared `ToolExecutor::is_mutating` default conservative by
returning `true`
- update the trait docs to say read-only tools should opt out explicitly
- add a regression test covering the default behavior
## Why
Hosts use this signal for serialization and approval policy. Treating
unknown contributed tools as read-only lets a write-capable tool
accidentally bypass mutating-tool safeguards if it forgets to override
the hook.
## Validation
- not run, per request
## Why
The tool-extraction work needs one shared executable-tool seam that
hosts and tool owners can depend on without reaching into `codex-core`.
Landing that seam first makes the later tool-family ports incremental
and keeps the reusable contract separate from any one migration.
## What changed
- add a new `codex-tool-api` crate and workspace wiring
- move the common executable-tool contracts into that crate:
`ToolBundle`, `ToolDefinition`, `ToolExecutor`, `ToolCall`, `ToolInput`,
`ToolOutput`, `JsonToolOutput`, and `ToolError`
- keep host state generic through `ToolBundle<C>` / `ToolCall<C>` so
later integrations can provide their own runtime context without baking
core types into the API
- carry the host signals the runtime will need later, including
parallel-call support and mutability probing
- leave existing tool families in place for now; this PR only
establishes the reusable API surface
- add the Bazel target and lockfile updates for the new crate
## Testing
- `cargo test -p codex-tool-api`
