Agent directory

An agent directory is a searchable listing of agents, organized by category, capability or provider, that people and client agents use to find an agent for a job.

Directory and registry. Products use the two names loosely. A useful split: a registry is the source of record for who owns which identifier and endpoint, and a directory is built for finding and comparing, often adding curation, reviews or ratings. The MCP project’s documentation draws the same line for MCP servers. Its official registry holds deliberately unopinionated metadata, and it expects downstream aggregators, such as marketplaces, to add curation and community ratings on top.

How entries describe agents. For A2A agents the natural entry is the Agent Card. The A2A Agent Discovery guide describes catalogs that clients query by skills, tags, provider name or capabilities, and notes that A2A does not standardize the catalog API. Other projects define their own record formats. The AGNTCY project’s Directory, for example, describes agents with the Open Agentic Schema Framework (OASF), organizes capabilities in hierarchical taxonomies to match them against requirements, signs records for integrity and provenance, and distributes them across a peer-to-peer network using a distributed hash table.

What a listing tells you. A listing shows that an agent was added; it carries weight only as far as the directory says what it checked. Questions worth asking of any directory:

• Did it verify that the provider controls the domain the listing points to?
• Does it check Agent Card signatures, and against which keys?
• How does it handle abuse reports and entries whose endpoints stop answering?

Public and private. The A2A guide warns that Agent Cards can reveal internal URLs and descriptions of sensitive skills. It recommends authenticated access for such cards and describes registries that disclose different cards to different clients, which is why many directories of business agents are private.

Neighbouring terms. Agent discovery is the wider process a directory supports. Capability matching ranks directory results against a specific task.