How OSD works

Open Service Directory (OSD) has two halves:

• Publishing. A business describes its support agents in OSD brand listings, composed of a osd:brandName and osd:brandDomain, publishes them on its domain, and can submit them to an OSD registry.
• Discovering. An assistant reads the business’ brand listings or searches a registry. It checks the business’ endorsement, selects an agent, and connects through the agent’s protocol.

flowchart TD
    I["Assistant identifies a support need"] -->|Known domain| B["Read brand manifest"]
    I -->|Search by brand or task| R["Search OSD registry"]
    R --> C["Compare candidate with brand manifest"]
    C -->|Match| T["Assess trust and select an endorsed agent"]
    C -->|Mismatch or inconclusive| N["Reject, retry, or seek more evidence"]
    B --> T
    T --> X["Connect to support agent through MCP or A2A"]

1. Describe the support agent

The agent has a protocol-specific description, such as an MCP Server Card or an A2A Agent Card, that tells a compatible assistant how to connect.

An OSD listing describes the agent for discovery and names the brand it represents. It references the card or includes it inline.

2. Publish the listing

The brand publishes its listings in an ARD manifest:

https://{brand-domain}/.well-known/ard.json

The manifest contains an entries array. Publishing an entry there is the business’ endorsement of the agent it describes.

The business can maintain the manifest itself or authorize a support platform to manage it. The agent and its card may be hosted elsewhere. The endorsed listing is served from the brand’s domain.

The business can also submit the same listing to an OSD registry, which checks it against the brand’s publication before making it searchable.

3. Discover support agents

The assistant identifies the customer’s need and the brand. For a canceled flight, the itinerary names the airline. If the business or brand is unclear, the assistant asks or searches for possible matches.

With a known domain, the assistant reads the manifest directly. Otherwise it searches a registry by brand or support need. Registry results include each brand listing, its source registry, and a relevance score.

4. Check endorsement and select an agent

A listing read from the business’ validated manifest is already endorsed. A registry candidate is endorsed only if it matches an entry in the business’ ARD manifest. See trust model for the rule and its outcomes.

The assistant then picks the agent that fits the request. If none fits, or the business is still uncertain, it tries another candidate, asks the customer, or stops.

5. Connect to the support agent

The assistant retrieves the agent’s card, or reads it inline, and connects using the advertised protocol. The agent handles authentication, permissions, and the operations it offers, such as returning rebooking options and submitting a change after the customer confirms.