Fix AI-generated JSON, Markdown
and prompts in seconds.

Trusted tools for AI developers.
Local-first. Deterministic. Open source.

🔧 Repair JSON 📝 Render Markdown 📊 Count Tokens 🔀 Convert Data
Try It Free How It Works
17
Capabilities
152
Tests Passing
100%
Browser
0
Network Calls
⚡ Instant JSON Repair Demo
{name:"Tom",}
AI output — broken
→
{"name":"Tom"}
CapabilityBase — fixed

Trusted by Design

Every capability is built on guarantees you can verify.

✅ Deterministic
🔒 Local First
🧪 Tested
🌐 Browser Only
📋 Versioned
📚 Open Source

Popular Tools

Start with the most-used capabilities. Zero setup.

🔧

JSON Repair

Fix broken JSON from AI output — trailing commas, single quotes, unquoted keys.

Open tool →
📝

Markdown Render

Render Markdown to clean HTML. XSS-safe. Zero dependencies. ~3KB.

Open tool →
📄

Markdown to HTML

Export Markdown as fragment, styled, or full HTML document.

Open tool →
🔀

Base64 Converter

Encode/decode text and images. All processing local in your browser.

Open tool →

Browse all 21 capabilities ↓

Why Deterministic?

AI generates. CapabilityBase verifies.

AI returned invalid JSON?

LLMs output JSON that looks right but fails to parse. CapabilityBase repairs it deterministically — same input, same output, every time.

Prompt too long?

Count tokens before sending. Know your cost before you pay. No API call needed.

Need HTML output?

AI writes Markdown. Your app needs HTML. Convert instantly with zero dependencies.

Want privacy?

Your data never leaves your device. No servers. No tracking. No API keys. Ever.

Capability Families

Organized by domain. Every family is a complete toolkit.

{ }
JSON
3/3
✅Repair
✅Format
✅Validate
Md
Markdown
4/4
✅Render
✅to HTML
✅to Image
✅HTML to Image
Tt
Text
6/6
✅Case Convert
✅Text Case
✅Sort Lines
✅Deduplicate
✅Remove Empty
✅Fullwidth ↔ Halfwidth
🔐
Encoding
3/3
✅Base64
✅Base64 Encode
✅URL Encode
🧠
AI / LLM
1/1
✅Token Counter
🎲
Generators
3/3
✅Password
✅Lorem Ipsum
✅UUID
🔒
Security
1/1
✅JWT Decoder

Architecture

One implementation. Every access method. Same deterministic result.

    AI / Agent / Workflow
            │
    ┌──────┐
    │ Adapters │   MCP · REST · SDK · CLI
    │└──────┘
            │
    ┌──────────────────────────────┐
    │  CapabilityBase Runtime             │
    │  Registry · Graph · Quality Pipeline   │
    │└──────────────────────────────┘
            │
    JSON · Text · Markdown · Image · Encode · Date
Build once. Run everywhere. Trust always.
Web · API · SDK · CLI · MCP · Workflow

Every CapabilityBase tool you use in the browser is powered by the same engine. A single deterministic implementation is defined once, registered in a capability catalog, and served through whichever interface you — or your agent — call it from. No model. No server. No surprise.

Runtime — the engine

Pure, dependency-free JavaScript cores that repair, transform, and validate your data. Each core runs identically in the browser, Node, Edge, and Workers — same input, same output, every time. Zero network calls, zero AI inference.

Registry — the catalog

Maps every capability ID (like json.repair) to its implementation, semantic version, and contract. One definition becomes the single source of truth that every surface — web, SDK, or agent — reads from.

Adapters — the interface

The layer that exposes the runtime through different front doors. The Web UI is live today; the same core is built to be reached via MCP, REST, SDK, and CLI so any agent or workflow can call a capability by ID.

An agent calls a capability by ID

{
  "tool": "capabilitybase.json_repair",
  "input": { "json": "{ \"name\": \"AI\", }" }
}
→ Runtime routes to the json.repair core
→ Returns clean, deterministic JSON
→ No model. No API key. ~0.01ms.

One implementation. Every access method. Identical result — whether a human pastes JSON in the browser or an agent invokes it over MCP.