How is agents.json different from OpenAPI or standard function-calling?

agents.json is an open spec specifically for AI agents, describing not just individual endpoints but multi-step workflows that chain calls together. It follows a familiar declarative pattern like OpenAPI, but targets agent-side discovery and execution rather than traditional API clients.

Wildcard AI / agents.jsonOpen spec and platform that lets AI agents discover and call API workflows through an agents.json file.

5.0 (6)

Reviewed by Daniel Nikulshyn·Updated May 2026

Open Source Developer Tools AI Agents API Specification Workflow Automation Integration

Overview

Wildcard AI maintains agents.json, an open-source specification that describes how AI agents can find and invoke API endpoints and multi-step workflows. Instead of hardcoding tool calls or relying on brittle prompt engineering, developers publish an agents.json file alongside their API so any compatible agent can understand what actions are available and how to chain them. The accompanying platform helps teams author, host, and test these specs, and provides runtime tooling for agents to parse agents.json and execute the described workflows against real APIs. It aims to do for AI agents what OpenAPI did for traditional API clients, making integrations more declarative and reusable. It is well suited to developers building agentic applications, API providers who want their services to be agent-ready, and teams looking for a standard alternative to per-model function calling formats.

Key features

agents.json specification for describing API actions
Workflow definitions for chaining multiple endpoints
Runtime libraries for agent-side discovery and execution
Hosting and authoring tools for agents.json files
Compatibility with existing REST APIs and auth schemes
Open-source community and reference implementations

Pricing

Model: Freemium
Category: AI Agent Development Frameworks
Rating: 5.0 / 5 (6)

Use cases

Expose a SaaS API to AI Agents

Publish an agents.json file alongside an existing REST API so any compatible AI agent can discover available actions and call them without custom integration code.

Define Multi-Step API Workflows

Describe chained endpoint calls as reusable workflows in agents.json, letting agents execute complex sequences reliably instead of inferring steps through prompts.

Replace Brittle Prompt-Based Tool Use

Use the runtime libraries to give agents declarative, structured tool definitions, reducing failures caused by hardcoded tool calls or prompt engineering drift.

Author and Host Agent Specs

Teams can use the platform's authoring and hosting tools to create, test, and serve agents.json files, similar to how OpenAPI specs are managed for traditional clients.

Pros & Cons

Pros

Open-source and vendor-neutral specification
Reduces reliance on fragile prompt-based tool use
Supports multi-step API workflows, not just single calls
Familiar pattern for teams already using OpenAPI

Cons

Standard is still emerging and not widely adopted
Requires API providers to author and maintain a spec
Smaller ecosystem than proprietary function-calling tools

Reviews

5.0

Average from 6 ratings.

Aaliyah Johnson

May 4, 2026

Use it every day

Honestly didn't expect to like it this much. Runtime libraries for agent-side discovery and execution is exactly what I needed, and supports multi-step API workflows, not just single calls. but I reach for it almost every day now and it just clicks.

Jamal Carter

Sep 19, 2025

Years in this space

I've evaluated a lot of these over the years. What stands out here is runtime libraries for agent-side discovery and execution — handled better than most — and familiar pattern for teams already using OpenAPI. Worth the time if this is your use case.

Carlos Mendoza

Sep 18, 2025

Does the job

Pretty happy overall. Agents.json specification for describing API actions just works and reduces reliance on fragile prompt-based tool use. but no dealbreakers — I'd recommend it to a friend without hesitating.

Hiroshi Tanaka

Sep 8, 2025

Years in this space

I've evaluated a lot of these over the years. What stands out here is hosting and authoring tools for agents.json files — handled better than most — and reduces reliance on fragile prompt-based tool use. Worth the time if this is your use case.

Leila Hassan

Aug 12, 2025

Years in this space

Ahmed Saleh

Jun 13, 2025

Does the job

Pretty happy overall. Agents.json specification for describing API actions just works and supports multi-step API workflows, not just single calls. Standard is still emerging and not widely adopted can be annoying, but no dealbreakers — I'd recommend it to a friend without hesitating.

Q&A

What are the key benefits?

Benefits include reduced reliance on prompt-based tool use, support for multi-step workflows, and a familiar pattern for OpenAPI users.

Asked by Larisa Ionescu · Mar 10, 2026

Is agents.json production-ready and widely supported?

The specification is open-source and vendor-neutral with reference implementations, but it's still emerging and has a smaller ecosystem than proprietary function-calling tools. It's best suited to developers comfortable adopting early standards for agentic applications.

Asked by Diego Fernández · Feb 11, 2026

Is Wildcard AI open-source?

Yes, Wildcard AI is open-source and vendor-neutral.

Asked by Sami Virtanen · Dec 18, 2025

What problem does it solve?

It reduces reliance on fragile prompt-based tool use and supports multi-step API workflows.

Asked by Quang Nguyen · Dec 18, 2025

What do I need to do as an API provider to support Wildcard AI?

You author and host an agents.json file alongside your existing REST API, describing available actions and workflows. Wildcard provides authoring, hosting, and testing tools, and the spec is compatible with existing REST endpoints and auth schemes, so you don't need to rebuild your API.

Asked by Sanjay Gupta · Dec 13, 2025