devtools.codes

Task guides

15 questions answered in full, each with the tool that answers it built into the page.

Token & Cost Calculator

Estimate token usage and monthly API costs.

JSON Schema Builder

Build a schema visually and export it as a tool definition.

Structured Output Validator

Check model output against a schema, with the path that broke.

Instruction File Generator

One form, four agent instruction files that agree on every fact.

MCP Config Validator

Catch the mistakes that break an MCP config in practice.

RAG Chunking Playground

See the chunks your settings actually produce, before you index.

Secret & API Key Scanner

Find leaked keys before you commit. No ads on this page.

How these differ from the tool pages

A tool page is organised around an instrument: what it does, how to drive it, and what its settings mean. A task page is organised around a question someone actually asked, and it embeds whichever tool answers that question directly at the top. If you already know which tool you want, the catalogue is the faster route. If you have a problem and no particular tool in mind, start here.

The distinction matters most when the answer is partly judgement. Knowing how to run a chunking preview is a tool question. Knowing how much overlap is worth paying for, and how to tell when you have too much, is a task question, and no interface can answer it on its own. These pages carry the reasoning that sits around the tool rather than inside it.

What these pages cover

Four groups, following the shape of the work. Counting and costing covers tokens, per-request pricing and building an estimate you can defend before any code exists. Schemas and structured output covers writing a schema a model will actually follow, reading a validation failure, and the two provider tool-definition formats that wrap the same JSON Schema in different clothes.

Agent instruction files cover what belongs in AGENTS.md, what does not, and how to keep a second file from contradicting the first. Configuration and credentials covers the five things that stop an MCP server connecting, how to catch a key before it reaches a commit, and what to do in what order once one already has.

Using a task page

Each page is written to be read in a few minutes and to stand on its own if the embedded tool were removed. The explanation is the substance; the tool is there so you can finish the job without moving to another page and losing your place. Nothing you type into one of these pages is uploaded, exactly as on the tool pages themselves.

Pages that address adjacent questions link to one another, so following a thread through a subject usually works better than returning here between steps. Where a page relates to a tool, the full tool page is linked at the foot of it, with the instructions, the worked example and the settings the shorter page does not repeat.