Concepts › II.

Context

Reference: Context

Context lets you pass runtime data into an agent’s execution — user info, session state, feature flags, or any other data your agent needs.

Passing context


await agent.run("Hello", {
  context: {
    userId: "user_123",
    username: "Tony",
    preferences: { theme: "dark" },
  },
});

Using context in instructions

Instructions can be a function that receives the context:


import { Agent } from "kernl";
import { anthropic } from "@kernl-sdk/ai/anthropic";
 
const agent = new Agent({
  id: "assistant",
  name: "Assistant",
  model: anthropic("claude-sonnet-4-5"),
  instructions: (ctx) => `
    You are helping ${ctx.context.username}.
    Their user ID is ${ctx.context.userId}.
  `,
});

Type-safe context

Define a context type for type safety:


import { Agent } from "kernl";
import { anthropic } from "@kernl-sdk/ai/anthropic";
 
interface UserContext {
  userId: string;
  username: string;
  preferences: { theme: string };
};
 
const agent = new Agent<UserContext>({
  id: "assistant",
  name: "Assistant",
  model: anthropic("claude-sonnet-4-5"),
  instructions: (ctx) => `You are helping ${ctx.context.username}.`,
});
 
// Typescript knows what context expects
await agent.run("Hello", {
  context: {
    userId: "user_123",
    username: "Tony",
    preferences: { theme: "dark" },
  },
});

Accessing context in tools

Tools also have access to context:


import { tool } from "kernl";
import { z } from "zod";
 
const greet = tool({
  id: "greet",
  description: "Greet the user by name",
  parameters: z.object({}),
  execute: async (ctx) => {
    return `Hello, ${ctx.context.username}!`;
  },
});