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glm-5.1 27e2763d02 Clarify Zod requirement for tool args, document Zod vs TypeBox layers

OpenCode's registry calls z.object(def.args) on every plugin tool definition,
so Zod is mandatory for the tool schema — no JSON Schema escape hatch. TypeBox
is used for our own config validation where we control the schema. The two
serve different layers with different constraints. Updated both the overview
and ADR-001 with a clear table showing which library serves which concern.

2026-04-29 07:36:23 +00:00

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status	last_updated
draft	2026-04-28

ADR-001: Registry Pattern (Single Tool Dispatch)

Context

The plugin exposes 14 distinct operations (list, show, deps, dependents, validate, topo, cycles, critical, parallel, bottleneck, risk, cost, decompose, help). OpenCode's tool system adds each tool's JSON schema to the system prompt. At ~200-300 tokens per tool definition, 14 individual tools would consume ~3500 tokens of context before the agent even starts working.

Decision

Collapse all operations into a single taskgraph tool that dispatches by {op, args}. The agent calls taskgraph({op: "help"}) to discover available operations on demand.

The dispatch field is named op (operation) rather than tool to avoid collision with OpenCode's own "tool" terminology. An agent calling taskgraph({op: "list"}) reads clearly: "run the list operation on the taskgraph." This also matches the Rust CLI's subcommand pattern (taskgraph parallel, taskgraph critical).

This follows the pattern established by open-memory, which exposes 9 operations through a single memory tool.

Consequences

Positive:

Minimal context overhead (~250 tokens for one tool schema vs ~3500 for 14)
Adding new operations never increases context bloat
Agent always has access to the full operation set without schema pollution
Consistent with the alk.dev ecosystem pattern (memory, coordinator both use this)
op field name is unambiguous in OpenCode's context

Negative:

The op and args fields are not individually validated by the outer Zod schema — validation happens inside the dispatch handler
Agent must call help to discover operations; the tool description can only hint
Slightly more overhead per call (string dispatch vs direct function call)

Mitigation for negatives:

The op field description enumerates all operation names, so the LLM can dispatch correctly
Validation errors are clear and include usage guidance
The help operation provides complete reference with examples

Zod Requirement

The tool args schema must use Zod because OpenCode's registry calls z.object(def.args) on every plugin tool definition. There is no JSON Schema alternative for tool definitions — this is the SDK's contract. TypeBox is used for internal config validation where we control the schema, but the tool definition boundary requires Zod. This is a small surface area (one schema for one tool) and doesn't extend beyond the taskgraph tool definition.

Note on Schema Libraries

The tool's outer parameter schema uses Zod (from @opencode-ai/plugin's tool() helper) because that's what OpenCode's plugin SDK provides for tool definitions. The plugin's internal config schema uses TypeBox (from @alkdev/typebox, already a dependency via @alkdev/taskgraph) for compile-time types and runtime Value.Check(). These are two different concerns: Zod for OpenCode's tool interface, TypeBox for our own config. No conflict — each is used where it's the native choice.

References

open-memory src/tools.ts: proven pattern in production
OpenCode plugin SDK: tool.schema (Zod) for tool parameter schemas
ADR-007: naming decision — taskgraph not tasks, op not tool

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