Module validate 

Do the emitted tool calls actually match the schemas the client advertised?

Tier B — Policy (ADR 0001). llama-server has no view of what a client does with a malformed call, so deciding whether to forward one is gglib’s call regardless of how good upstream’s grammar becomes. Nothing here is gated on RuntimeCapabilities.

Why this exists

tool_choice: "auto" is the path every agentic client uses, and on some model/build pairs llama.cpp installs no grammar for it. Measured on b10327 (ADR 0002, findings 4-5):

model	auto conformance	required conformance
Qwen3.5-4B	30/30	30/30
Llama 3.2 3B	≤ 4/30	30/30

On Llama 3.2, 26 of 30 calls put max_lines as the string "42" where the schema declares an integer. The client’s executor then fails, reports the error back to the model, and the model tries again — one of the ways a local agentic session dies, and nothing in gglib noticed it happening.

This module is the detection half. The repair half — re-issuing under a grammar, upstream’s with tool_choice: "required" or gglib’s own on a turn it constrained — lives in the proxy, because only it can make a second request. See Tool-call repair.

Deliberately not a JSON Schema engine

Only the constraint kinds small models demonstrably get wrong are checked: types, required, enum, additionalProperties: false, and the same checks recursively through nested objects and array items.

$ref, anyOf/oneOf/allOf, not, $defs and prefixItems yield Verdict::Unvalidatable and the response is forwarded untouched, and pattern is not checked at all. Half-implementing those constructs would produce false violations, and a false violation costs a wasted generation and replaces a working call with a re-rolled one.

Recursion is not optional

The experiment that motivated this module checked nested presence but not nested types, so options: {"follow_symlinks": "null"} passed a validator that should have rejected it and the measured conformance rate came out flattering. Pinned by validate_tests::a_nested_wrong_type_is_caught so the same gap cannot reappear where it would cost a real repair.

Structs

Violation

What a single tool call got wrong.

Enums

Verdict

The outcome of validating one response’s tool calls.

ViolationKind

The constraint a Violation broke.

Constants

SUBSCHEMA_KEYWORDS 🔒

Where a schema holds subschemas, besides the values of properties.

UNSUPPORTED_KEYWORDS 🔒

Schema keywords this validator does not implement.

Functions

check_object 🔒

The object-shaped checks: required, declared properties, and additionalProperties: false.

check_value 🔒

Check value against schema, appending (pointer, kind) for each violation found at or below this point.

schema_for 🔒

The parameters schema for name, from the advertised tools.

type_label 🔒

The type keyword as a violation names it: integer, or string or null.

type_matches 🔒

Whether value satisfies one JSON Schema type name.

type_name 🔒

The JSON type name of value, for violation reporting.

type_satisfied 🔒

Whether value satisfies a type keyword, written as one type or a list.

unsupported_reason 🔒

The first unsupported keyword in schema or in a subschema under it.

validate_tool_calls

Validate a response’s tool_calls against the request’s tools.