AI SDK middleware for parsing tool calls from models that do not natively support tools.

Install

pnpm add @ai-sdk-tool/parser

AI SDK compatibility

Fact-checked from this repo CHANGELOG.md and npm release metadata (as of 2026-02-18).

| @ai-sdk-tool/parser major | AI SDK major | Maintenance status | |---|---|---| | v1.x | v4.x | Legacy (not actively maintained) | | v2.x | v5.x | Legacy (not actively maintained) | | v3.x | v6.x | Legacy (not actively maintained) | | v4.x | v6.x | Active (current latest line) |

Note: there is no separate formal EOL announcement in releases/changelog for v1-v3; "legacy" here means non-current release lines.

Package map

| Import | Purpose | |---|---| | @ai-sdk-tool/parser | Main middleware factory, preconfigured middleware, protocol exports | | @ai-sdk-tool/parser/community | Community middleware (Sijawara, UI-TARS) |

Quick start

import { createOpenAICompatible } from "@ai-sdk/openai-compatible";
import { morphXmlToolMiddleware } from "@ai-sdk-tool/parser";
import { stepCountIs, streamText, wrapLanguageModel } from "ai";
import { z } from "zod";

const model = createOpenAICompatible({
  name: "openrouter",
  apiKey: process.env.OPENROUTER_API_KEY,
  baseURL: "https://openrouter.ai/api/v1",
})("arcee-ai/trinity-large-preview:free");

const result = streamText({
  model: wrapLanguageModel({
    model,
    middleware: morphXmlToolMiddleware,
  }),
  stopWhen: stepCountIs(4),
  prompt: "What is the weather in Seoul?",
  tools: {
    get_weather: {
      description: "Get weather by city name",
      inputSchema: z.object({ city: z.string() }),
      execute: async ({ city }) => ({ city, condition: "sunny", celsius: 23 }),
    },
  },
});

for await (const part of result.fullStream) {
  // text-delta / tool-input-start / tool-input-delta / tool-input-end / tool-call / tool-result
}

Choose middleware

Use the preconfigured middleware exports from src/preconfigured-middleware.ts:

| Middleware | Best for | |---|---| | hermesToolMiddleware | JSON-style tool payloads | | morphXmlToolMiddleware | XML-style payloads with schema-aware coercion | | yamlXmlToolMiddleware | XML tool tags + YAML bodies | | qwen3CoderToolMiddleware | Qwen/UI-TARS style <tool_call> markup |

Build custom middleware

import { createToolMiddleware, qwen3CoderProtocol } from "@ai-sdk-tool/parser";

export const myToolMiddleware = createToolMiddleware({
  protocol: qwen3CoderProtocol,
  toolSystemPromptTemplate: (tools) =>
    `Use these tools and emit <tool_call> blocks only: ${JSON.stringify(tools)}`,
});

Streaming semantics

• Stream parsers emit tool-input-start, tool-input-delta, and tool-input-end when a tool input can be incrementally reconstructed.
• tool-input-start.id, tool-input-end.id, and final tool-call.toolCallId are reconciled to the same ID.
• emitRawToolCallTextOnError defaults to false; malformed tool-call markup is suppressed from text-delta unless explicitly enabled.

Configure parser error behavior through providerOptions.toolCallMiddleware:

const result = streamText({
  // ...
  providerOptions: {
    toolCallMiddleware: {
      onError: (message, metadata) => {
        console.warn(message, metadata);
      },
      emitRawToolCallTextOnError: false,
    },
  },
});

Local development

pnpm build
pnpm test
pnpm check:biome
pnpm check:types
pnpm check

Examples in this repo

• Parser middleware examples: examples/parser-core/README.md
• RXML examples: examples/rxml-core/README.md

Run one example from repo root:

pnpm dlx tsx examples/parser-core/src/01-stream-tool-call.ts