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codex/codex-rs/tools/src
Celia Chen 464ab40dfa feat: best-effort compact large tool schemas (#23904)
## Why

The `dev/cc/ref-def` branch preserves richer JSON Schema detail for
connector tools, including `$defs` and nested shapes. That improves
fidelity, but it pushes the largest connector schemas well past the
intended tool-schema budget. This PR adds a best-effort compaction pass
for unusually large tool input schemas so the p99 and max tails stay
small while ordinary schemas are left alone.

## What Changed

- Added best-effort large-schema compaction in
`codex-rs/tools/src/json_schema.rs` after schema sanitization and
definition pruning.
- Compaction runs as a waterfall only while the compact JSON budget
proxy is exceeded:
  1. Strip schema `description` metadata.
  2. Drop root `$defs` / `definitions`.
  3. Collapse deep nested complex schema objects to `{}`.
- Kept top-level argument names and immediate schema shape where
possible.

## Corpus Results

Scope: 2,025 schemas under `golden_schemas`, all parsed successfully.
Token count is `o200k_base` over compact JSON from
`parse_tool_input_schema`.

| Percentile | Before `origin/main` `4dbca61e20` | After branch
`dev/cc/ref-def` `f9bf071758` | After this PR |
|---|---:|---:|---:|
| p0 | 9 | 9 | 9 |
| p10 | 59 | 63 | 63 |
| p25 | 81 | 86 | 86 |
| p50 | 114 | 127 | 125 |
| p75 | 174 | 205 | 202 |
| p90 | 295 | 335 | 322 |
| p95 | 391 | 526 | 422 |
| p99 | 794 | 1,303 | 689 |
| max | 2,836 | 3,337 | 887 |

After this PR, `0 / 2,025` schemas are over 1k tokens.

### Compaction Savings

These are cumulative waterfall stages over the same corpus. Later passes
only run for schemas that are still over the compact JSON budget proxy.

| Stage | Total tokens | Step savings | Schemas changed by step |
|---|---:|---:|---:|
| No compaction | 391,862 | - | - |
| Strip schema `description` metadata | 350,961 | 40,901 | 66 |
| Drop root `$defs` / `definitions` | 340,683 | 10,278 | 13 |
| Collapse deep complex schemas to `{}` | 335,875 | 4,808 | 6 |
2026-05-22 01:26:17 +00:00
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