Agent builders comparing MCP, A2A, OpenAPI and x402 before choosing an adapter
Agent discovery
How autonomous agents discover and integrate capabilities.
A standards-first route for choosing MCP, A2A, OpenAPI or x402 from a declared job instead of guessing from undocumented prompts.
Delx publishes an institutional ARD catalog and property-owned machine contracts so an agent can classify an intent, resolve the right surface, inspect schema and policy, then choose MCP for tools, A2A for agent-to-agent exchange or OpenAPI/x402 for a paid HTTP capability. Discovery informs a decision; it does not authorize a spend or promise a result.
Outcome
A precise job, not a generic promise.
Make the first integration step reproducible: one intent, one owner, one canonical contract and an explicit decision before execution.
Teams that need a machine-readable starting point for a new capability
Operators that want discovery, authorization, execution and verification to remain separate decisions
Live capability map
Start from a governed contract.
Each capability links to the property that owns its current terms. Inspect that source immediately before execution.
Institutional ARD catalog
Resolve the Delx ecosystem graph and follow each capability to the property that owns its current terms.
Inspect the contract →MCP server card
Inspect the tool-oriented JSON-RPC entry point and the published server metadata before connecting an MCP client.
Inspect the contract →A2A agent card
Read the agent identity, skills and peer-discovery contract for agent-to-agent workflows.
Inspect the contract →OpenAPI + x402 terms
Inspect HTTP schemas and payment requirements for a caller that is ready to evaluate a paid capability.
Inspect the contract →Execution
Readable by a person. Runnable by an agent.
The same path can be evaluated manually, embedded in a toolchain or followed autonomously within a bounded authorization.
- Classify the jobState the required outcome and whether the work needs a tool call, an agent handoff or a paid HTTP result.
- Resolve the ownerStart at the ARD catalog, then follow the link to the Protocol, Commerce or another focused Delx property.
- Inspect the contractRead the current card or schema, including inputs, outputs, policy, price, delivery and known limits.
- Select and verifyChoose the protocol that fits, authorize only the declared scope and retain result provenance after execution.
curl · inspect the discovery graph
curl -sS https://delx.ai/.well-known/ai-catalog.jsonEvidence
What can be verified.
- The institutional ARD catalog, MCP server card, A2A card and paid OpenAPI are public machine contracts that can be inspected independently.
- The Protocol and Commerce surfaces keep separate ownership, metrics and terms; the discovery graph links between them instead of flattening them into one catalog.
- The developer path publishes standards-oriented entry points without requiring a proprietary Delx SDK.
Boundaries
What is not being claimed.
- Discovery metadata does not grant authorization, create an account or approve a payment; the caller must make that decision from the current contract.
- MCP, A2A, OpenAPI and x402 are different integration surfaces. A catalog entry does not imply that every capability supports every protocol.
- A machine-readable summary is a starting point, not a substitute for the linked schema, price, source permissions or delivery terms.
Direct answers
Questions agents and evaluators ask.
Visible answers mirror the structured data on this page.
What is agent discovery?
Agent discovery is the step where an autonomous system resolves a capability, its owner and its current machine contract before it chooses an integration or authorizes execution.
When should an agent use MCP, A2A or OpenAPI/x402?
Use MCP when the job is a tool call over a model-context connection, A2A when agents need a peer-to-peer task or handoff contract, and OpenAPI/x402 when a paid HTTP capability publishes the right schema and payment terms. Inspect the specific service before deciding.
Where should an agent start with Delx?
Start with the institutional ARD catalog at delx.ai/.well-known/ai-catalog.json, follow the property-owned link, then inspect the MCP server card, A2A agent card or paid OpenAPI that matches the job.
Does discovering a Delx capability authorize a payment?
No. Discovery is read-only orientation. Payment, credentials, scope and execution remain explicit caller decisions governed by the linked service contract.