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Migrating from raw WebMCP

Add Agentronics to a site that already registers WebMCP tools with document.modelContext.

Migrating from raw WebMCP

If your site already calls document.modelContext.registerTool(...), Agentronics wraps that surface — it doesn't replace your tools. You keep your implementations and gain detection, authentication, authorization (including review), per-tool status, procedural memory and observability.

What changes

Stays the sameNow goes through Agentronics
name, title, description, inputSchema, annotationsEach call is checked against your rules first (allow / review / deny)
Your execute logic and return valuesThe session is attributed to the agent that called
WebMCP agents keep working unchangedRegistration status and call outcomes are traced to the console
Approved descriptions from the console can replace the text agents see

Pattern 1 — move registrations into the SDK

Before:

const controller = new AbortController()
await document.modelContext.registerTool(
  {
    name: 'add_to_cart',
    title: 'Add to cart',
    description: 'Add a product to the cart.',
    inputSchema: { type: 'object', properties: { productId: { type: 'string' } }, required: ['productId'] },
    async execute({ productId }, { signal }) {
      await addToCart(productId, { signal })
      return { ok: true }
    },
  },
  { signal: controller.signal }
)

After:

import { Agentronics } from '@agentronics/sdk'
 
const client = Agentronics.init({ publishableKey: 'agtx_pk_live_…', siteId: 'shop', policies, toolDescriptions })
 
client.registerTool({
  name: 'add_to_cart',
  title: 'Add to cart',
  description: 'Add a product to the cart.',
  inputSchema: { type: 'object', properties: { productId: { type: 'string' } }, required: ['productId'] },
  async execute({ productId }, { identity, signal }) {
    await addToCart(productId, { signal })
    return { ok: true }
  },
})
 
const { registrations } = client.publishToWebMcp()
// → [{ name: 'add_to_cart', status: 'callable' }]

The SDK owns the AbortControllers: it unregisters and re-registers when the set of tools a given agent may see changes. Drop your own registerTool calls once a tool moves over.

Pattern 2 — keep your registrations, add a policy check

If your registration code is hard to move, call evaluate() inside execute:

await document.modelContext.registerTool({
  name: 'add_to_cart',
  description: '…',
  async execute(input) {
    const decision = await client.evaluate('add_to_cart')
    if (decision.decision === 'deny') throw new Error(decision.reason)
    // decision.decision === 'review': ask the person yourself before continuing
    await addToCart(input.productId)
    client.notifyToolInvoked('add_to_cart')
    return { ok: true }
  },
})

You keep policy enforcement and traces, but lose automatic review prompts, per-tool status, approved descriptions and identity-based surfacing.

Pattern 3 — agents that click instead of calling tools

Browser-automation and vision agents use your UI directly. Mark the controls and install the enforcer:

client.installDomEnforcer()
 
<button data-agentronics-tool="checkout">Pay now</button>

Rules for checkout now apply to clicks from those agents too.

Declarative forms

The declarative API (<form toolname tooldescription>) was removed from the WebMCP spec in October 2026 and is only an explainer now. If you used it, register those forms as imperative tools that fill and submit the form — Agent Nic generates exactly that when it writes tools for your repo.

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Site memory cookbook

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