Tianyi Cui
605587e79c
Add a second axis to every RFC — its class (feature, bug-fix,
simplification, architecture, process, testing) — encoded in the path
as docs/rfc/{lifecycle}/{class}/file.md. The folder is the label, so
the closed set is enforced by structure rather than a parsed field.
Two new doc-sync gates back it:
- verify-rfc-classification: every RFC sits in a valid class folder and
the README index lists it under the matching lifecycle→class heading.
- verify-doc-refs: every docs/*.md path cited in a packages|examples TS
comment resolves — closes a drift class verify-md-links can't see, and
catches the four comment refs this reorg moved.
The README gains a Classification section explaining the taxonomy and
per-class index sub-sections. A self-referential process RFC records why
the scheme is path-encoded and gated.
23 lines
2.5 KiB
Markdown
23 lines
2.5 KiB
Markdown
# RFC: Runtime arg validation at the model boundary
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Status: implemented (accepted 2026-06-13)
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<!-- XXX: legacy ADR/RFC body format, not yet normalized to a unified RFC template. -->
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## Context
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`defineTool` ([the custom schema DSL](2026-06-11-custom-schema-dsl.md)) gives tool authors a typed `execute(args)` via the `InferArgs<S>` mapping. But that type is a compile-time claim about a value that arrives at runtime as model-generated JSON: nothing forced the model to honor the schema, so a malformed call — missing a required key, a string where a number was declared, an enum value outside the set — reached `execute` typed-in-name-only. The tool body then either crashed on the bad shape (a generic stack trace the model can't act on) or, worse, silently misbehaved. Meanwhile the converter already encodes the exact structure a validator would need to walk.
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## Decision
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`validateArgs(spec, args): string[]` interprets a `SchemaSpec` over a runtime value, returning human-readable violations (empty = valid), and is total (never throws). `defineTool` runs it before the typed body; on violations it throws `ToolArgsError` (`code: 'INVALID_ARGS'`, message listing the violations), which the registry's existing execute-waterfall catch turns into an `isError` result the model reads and self-corrects from.
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The validator mirrors `schemaSpecToJsonSchema` semantics exactly — same structure walked, same rules: top level must be a non-array object; required keys come only from `required: true`; extra keys are allowed (no `additionalProperties: false`); `default` is not applied; an `object`/`array` prop without `properties`/`items` only type-checks; `enum` is membership. Raw-registered (MCP) tools are not touched — they validate their own input.
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## Consequences
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- The model gets actionable feedback on its own malformed calls instead of an opaque crash, closing the gap between `InferArgs`'s promise and runtime reality.
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- The validator and `InferArgs` must stay in agreement; that drift risk is to be closed by a property test ([property-based testing](../testing/2026-06-11-property-based-testing.md), not yet landed) generating args that satisfy `InferArgs` and asserting they pass `validateArgs`. Until then the agreement rests on the example tests and the shared converter structure.
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- `ToolArgsError` is a plain `Error` with a `code` field for now; if a harness-wide error taxonomy lands it becomes a subclass without changing callers that read `.message`.
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- Validation cost is negligible next to a model call.
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