Files
shockbot/mcp/output.ts
T
Mateusz Burzyński 5684cbef77 Implement support for output schemas (#411)
* tweak examples

* tweak prompt

* Implement support for output schemas

* fix: add example for structured output with zod schema

* tweak

* remove redundant cast

* fix input name

* strip $schema

* hack around vendor requirement

* clarify required result output

---------

Co-authored-by: pullfrog[bot] <226033991+pullfrog[bot]@users.noreply.github.com>
2026-03-05 23:07:03 +00:00

85 lines
3.0 KiB
TypeScript

import type { StandardSchemaV1 } from "@standard-schema/spec";
import { Ajv } from "ajv";
import { type } from "arktype";
import { log } from "../utils/cli.ts";
import type { ToolContext } from "./server.ts";
import { execute, tool } from "./shared.ts";
export const SetOutputParams = type({
value: type.string.describe("the output value to expose as a GitHub Action output"),
});
type JsonSchema = Record<string, unknown>;
function jsonSchemaToStandardSchema({
$schema: _,
...jsonSchema
}: JsonSchema): StandardSchemaV1<any> & { toJsonSchema(): JsonSchema } {
const ajv = new Ajv();
const validate = ajv.compile(jsonSchema);
return {
"~standard": {
version: 1,
// xsschema (used by fastmcp) hardcodes supported vendors instead of duck-typing toJsonSchema().
// "arktype" works because its converter is just `(schema) => schema.toJsonSchema()`.
vendor: "arktype",
validate(input: unknown) {
if (validate(input)) {
return { value: input };
}
return {
issues: (validate.errors ?? []).map((err) => ({
message: `${err.instancePath || "/"}: ${err.message ?? "validation error"}`,
path: err.instancePath ? err.instancePath.split("/").filter(Boolean) : [],
})),
};
},
},
toJsonSchema() {
return jsonSchema;
},
};
}
function storeOutput(ctx: ToolContext, value: string) {
const selfId = ctx.toolState.selfSubagentId;
if (selfId) {
const subagent = ctx.toolState.subagents.get(selfId);
if (subagent) {
subagent.output = value;
log.debug(`set_output: routed to subagent ${selfId} (value=${value.slice(0, 80)})`);
return { success: true, routed: "subagent" as const };
}
log.warning(
`set_output: selfSubagentId=${selfId} but subagent not found in map — routing to action output`
);
}
ctx.toolState.output = value;
return { success: true, routed: "action_output" as const };
}
export function SetOutputTool(ctx: ToolContext, outputSchema?: JsonSchema) {
if (outputSchema) {
return tool({
name: "set_output",
description:
"Set the structured action output. You MUST call this tool before finishing — the output is required. Pass the output object directly as the tool arguments (no wrapping needed).",
parameters: jsonSchemaToStandardSchema(outputSchema),
execute: execute(async (params) => {
return storeOutput(ctx, JSON.stringify(params));
}),
});
}
return tool({
name: "set_output",
description:
"Set the action output. When called by a subagent, returns a summary result to the orchestrator — this is the ONLY way to pass results back. When called by the orchestrator in standalone mode (trigger: unknown), exposes the value as the 'result' GitHub Action output for downstream workflow steps. Do NOT use this for progress reporting — use report_progress instead.",
parameters: SetOutputParams,
execute: execute(async (params) => {
return storeOutput(ctx, params.value);
}),
});
}