A safe tool-schema migration defines the old and target contracts precisely, maps each action and field, updates every consumer, and proves accepted behavior through deterministic scenarios before production traffic changes.
Freeze the old and target contracts
A migration needs two immutable snapshots: the contract agents use today and the contract the runtime will support after release. Each snapshot includes names, descriptions, JSON Schema arguments, return shapes, error classes, authorization requirements, and version metadata. A moving target makes it impossible to distinguish migration defects from continuing product changes.
JSON Schema provides a vocabulary for types, required properties, combinations, formats, and annotations, but structural validity does not establish semantic equivalence. A renamed amount field may also change units, and an optional identifier may become required because the runtime no longer infers it. The map should record those meaning changes in ordinary language beside the schema diff.
Migrate consumers from one explicit map
Prompts, planners, generated programs, registries, fixtures, clients, and validators should consume one versioned contract source where possible. If a copy must remain, the build should derive it and compare its hash. This removes the common failure where the runtime updates while an old builder prompt continues teaching names that no longer exist.
Typed validators should check calls before dispatch and return errors the agent can interpret without guessing. A migration suite includes valid calls, missing required fields, extra fields, wrong types, retired names, ambiguous aliases, authorization failures, and representative tool results. Fixtures preserve the accepted inputs and outputs without depending on a live external service for every test.
Prove behavior beyond schema validation
Behavioral scenarios then ask whether the agent completes the task, chooses the intended tool, supplies valid arguments, handles the result, and stops correctly on terminal failures. Exact prose can vary, so the suite should assert stable facts and tool events rather than one expected sentence. Any stochastic judge remains secondary to deterministic contract checks.
Reality Contact, LLC can prepare and execute this migration for the agreed tool set. The buyer supplies the target semantics, approves deprecations and permissions, and controls canary traffic and release. The implementation does not choose business meaning when the old and target contracts disagree.
Where the service stops
Reality Contact, LLC implements and tests the migration, but does not invent target semantics, weaken authorization, approve external side effects, select production traffic, or retire a contract without buyer approval. The buyer approves the target semantics and caller set, runs the accepted canary scenarios, and retires the old contract only after compatibility and rollback gates pass. This is software migration and technical testing, and it does not replace legal, security, privacy, compliance, or professional advice. The buyer owns tool semantics, credentials, permissions, caller communication, canary authorization, production release, and contract retirement.
Sources: JSON Schema 2020-12 core specification; OpenAI function calling guide.