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Michael Bolin be5afc65d3 codex-tools: extract MCP schema adapters (#15928 )

## Why

`codex-tools` already owns the shared tool input schema model and parser
from the first extraction step, but `core/src/tools/spec.rs` still owned
the MCP-specific adapter that normalizes `rmcp::model::Tool` schemas and
wraps `structuredContent` into the call result output schema.

Keeping that adapter in `codex-core` means the reusable MCP schema path
is still split across crates, and the unit tests for that logic stay
anchored in `codex-core` even though the runtime orchestration does not
need to move yet.

This change takes the next small step by moving the reusable MCP schema
adapter into `codex-tools` while leaving `ResponsesApiTool` assembly in
`codex-core`.

## What changed

- added `tools/src/mcp_tool.rs` and sibling
`tools/src/mcp_tool_tests.rs`
- introduced `ParsedMcpTool`, `parse_mcp_tool()`, and
`mcp_call_tool_result_output_schema()` in `codex-tools`
- updated `core/src/tools/spec.rs` to consume parsed MCP tool parts from
`codex-tools`
- removed the now-redundant MCP schema unit tests from
`core/src/tools/spec_tests.rs`
- expanded `codex-rs/tools/README.md` to describe this second migration
step

## Test plan

- `cargo test -p codex-tools`
- `cargo test -p codex-core --lib tools::spec::`

2026-03-26 19:57:26 -07:00

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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 primitives that no longer need to live in core/src/tools/spec.rs:

JsonSchema
AdditionalProperties
parse_tool_input_schema()
ParsedMcpTool
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:

Move low-coupling tool primitives here.
Switch non-core consumers to depend on codex-tools directly.
Leave compatibility-sensitive adapters in codex-core while 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.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.

2.5 KiB Raw Blame History

codex-tools

Vision

Migration approach

Crate conventions

2.5 KiB

Raw Blame History