Build with AI

APIs, automation, agents, MCP, evaluation and improvement loops.

Build with AI

How do you move your Codex work off GPT-5.5?

GPT-5.5 left Codex on October 14 for everyone signed in with a ChatGPT account, so any default, saved setting, custom agent, scheduled task or script that still names gpt-5.5 needs a new model, usually…

4 min read

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How do you build with GPT-6.1 Sol in the API?

You call GPT-6.1 Sol through OpenAI's Responses API by setting the model to gpt-6.1-sol, choosing a reasoning effort, and putting the instructions you reuse at the start of every request so they can be served…

4 min read

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What is an agent harness?

An agent harness is the ordinary software wrapped around a language model that turns it into an agent: it runs the loop of asking the model what to do next, carries out the tool calls the model requests,…

4 min read

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How do you build a multi-agent workflow?

Split the job into stages that each have one clear goal, give each stage its own agent with narrow instructions and a fixed output format, and let your code pass the result of one agent to the next.

4 min read

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How do you use the Codex app on macOS?

Sign in with your ChatGPT account, add a project folder, and start one thread per task; each agent can work in its own copy of the code, and you review its changes as a diff before keeping them.

4 min read

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How do you use GPT-5-Codex for code review?

Turn on Codex code review for a GitHub repository, then either let it review each pull request automatically when it is marked ready, or ask for a review with a comment such as "@codex review for security…

4 min read

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How do you use Gemini CLI?

Install it with npm (it needs Node.js 20 or newer), type gemini in a project folder, sign in with a personal Google account, and describe what you want in plain language.

4 min read

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How do you write evals for an AI agent?

Write a set of realistic tasks, each with a check on the final state the agent should leave behind (the outcome) and, where it matters, a check on the tools it called along the way (the trajectory).

4 min read

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What is a coding agent?

A coding agent is an AI system that doesn't just suggest code but carries out a programming task itself: it reads your project, edits files, runs commands and tests, and repeats until the job is done or it…

4 min read

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How do you use Codex CLI in your terminal?

Install it with npm, set your OpenAI API key, open a terminal in your project folder and type codex followed by what you want done, such as "fix the failing test." It reads your files, proposes changes and…

4 min read

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How do you build your first MCP server?

Install the official MCP Python SDK, write a short file that creates a FastMCP server and turns one Python function into a tool with a decorator, then open it in the MCP Inspector to check it.

4 min read

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How do you evaluate a RAG system?

Test the two halves separately. First check whether retrieval finds the right passages for a fixed set of questions, then check whether the answers stick to those passages, and have a person review a sample…

4 min read

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Should you let an AI control your computer?

Not your everyday computer, not yet. Anthropic's computer use beta is worth exploring, but only inside a sealed-off test machine with no personal data, limited internet access and a person watching every run.

5 min read

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How does prompt caching cut API costs?

Prompt caching lets an AI provider remember the opening part of a prompt you send again and again, so later requests that start the same way are billed at a lower rate for that part.

5 min read

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How do you build an AI agent step by step?

Build it in six decisions: a narrow goal, a short list of tools, a loop that lets the model call those tools through function calling, a memory for what it has learned, firm stop rules, and a log of every…

3 min read

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What is prompt injection?

Prompt injection is an attack where text written by someone other than the app's builder, typed into a chat or hidden in a web page, email or document, gives a language model new instructions that override…

4 min read

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How does fine-tuning GPT-3 work?

Fine-tuning trains a private copy of a GPT-3 model on your own examples, each one a prompt paired with the completion you want, so the model learns your task and style instead of reading them from a long…

4 min read

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What can you build with the GPT-3 API?

With the GPT-3 API you can build almost any tool whose input and output are text, from a style rewriter or a question-answering helper to a chatbot character or a code sketch made from a plain description.

4 min read

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