agents.json vs Agentic Resource Discovery
They answer different questions: agents.json is a step 5 (Act) standard, Agentic Resource Discovery step 1 (Discover), so they are not substitutes.
| agents.json | Agentic Resource Discovery ARD | |
|---|---|---|
| Lifecycle step | 5 Act: Do something for me | 1 Discover: What is here, and where? |
| Answers | How does an agent learn which multi-step API call sequences ("flows") a service supports, on top of its raw OpenAPI surface? | Where are an organization's discoverable agentic resources (MCP servers, A2A agents, skills, registries), and how can they be found by search rather than pre-installed one at a time? |
| Governed by | Wildcard AI; single company controls the spec and the reference "Wildcard Bridge" runtime and maintains a discretionary registry of published files | Authored by individuals at Google, Microsoft and Hugging Face (Junjie Bu, R.V. Guha, Shaun Smith); published as an open GitHub project (ards-project/ard-spec) with no formal standards body yet; contributions acknowledged from AWS, Cisco, Databricks, GitHub, GoDaddy, Nvidia, Salesforce and Snowflake |
| Status (issuer's words) | Dormant: last push 2025-08-21, version 0.1.0 | Proposal |
| Phase | deprecated | draft |
| Version | 0.1.0 (2025-03) | v0.91 (2026-08-26) |
| Form / transport | well-known file | well-known file |
| Found at | /.well-known/agents.json (proposed; not mandatory, per the spec's own FAQ) | /.well-known/ard.json |
| Adoption | unmeasured | observed — agenticresources.dev own probe, 2026-09-04 |
| Evidence | 4 verified, 2 reported | 2 verified, 2 reported |
| Primary use case | Let agents discover my API or service | Let agents discover my API or service |
| Last verified | 2026-10-18 (current) | 2026-10-18 (current) |
| Specification | https://github.com/wild-card-ai/agents-json | https://raw.githubusercontent.com/ards-project/ard-spec/main/spec/ard.md |
When to use which
- Choose agents.json when your question is “How does an agent learn which multi-step API call sequences ("flows") a service supports, on top of its raw OpenAPI surface?” and you accept its maturity: phase deprecated, adoption unmeasured. It is no longer maintained; prefer its successor.
- Choose Agentic Resource Discovery when your question is “Where are an organization's discoverable agentic resources (MCP servers, A2A agents, skills, registries), and how can they be found by search rather than pre-installed one at a time?” and you accept its maturity: phase draft, adoption observed (agenticresources.dev own probe, 2026-09-04).
Read the full articles
- agents.json: How does an agent learn which multi-step API call sequences ("flows") a service supports, on top of its raw OpenAPI surface?
- Agentic Resource Discovery: Where are an organization's discoverable agentic resources (MCP servers, A2A agents, skills, registries), and how can they be found by search rather than pre-installed one at a time?