Agent Registry

Unified registry for discovering, managing, and monitoring A2A agents, MCP servers, and agentskills.io skills at enterprise scale.

Agent Registry

The Agent Registry provides a discovery layer for AI agents and tools. The core A2A Agent Registry is available now with full CRUD, fine-grained authorization, and event streaming.

The registry fills the explicit gap in the A2A specification, which acknowledges the need for curated registries but does not prescribe a standard API for them.

The A2A specification states: “The current A2A specification does not prescribe a standard API for curated registries” and “The A2A community explores standardizing registry interactions or advanced discovery protocols.” The Agent Registry is designed to fill this gap with enterprise-grade capabilities.

The Discovery Problem

The A2A protocol v1.0 defines three agent discovery strategies, two of which are limited:

Strategy	Limitation
Well-Known URI (/.well-known/agent-card.json)	Requires knowing the agent’s domain upfront
Curated Registries	Acknowledged as needed but explicitly unspecified
Direct Configuration	Hardcoded and inflexible

Meanwhile, the MCP ecosystem has its own public registry, and agentskills.io provides a portable skill format. These three ecosystems are complementary but fragmented — no unified discovery layer exists.

Key Capabilities

A2A Agent Registration (Available)

RESTful CRUD for Agent Cards with full schema validation, optimistic concurrency control, and fine-grained authorization. Agents can register, update, and manage their A2A-compliant Agent Cards through the registry API. Auto-detects A2A protocol version (0.3 vs 1.0) from card structure. SHA-256 card hash for duplicate detection.

API surface:

Method	Endpoint	Description
POST	/agents	Register agent (201 + Location + ETag)
GET	/agents	List with pagination, status/tag/version filters
GET	/agents/{resource_uri}	Get by URI (ETag)
PUT	/agents/{resource_uri}	Update card with If-Match version guard
DELETE	/agents/{resource_uri}	Permanent delete, cleans up authorization tuples
POST	/agents/validate	Dry-run card validation (no DB write)

Health Monitoring

Periodic multi-level health probes ensure agents are reachable and functioning:

Level	Check	Purpose
L1	Endpoint reachability	Is the agent’s URL responding?
L2	Card freshness	Has the Agent Card been updated recently?
L3	Protocol probe	Does the agent respond to A2A/MCP protocol requests?

All probes include SSRF protection to prevent internal network scanning.

Lifecycle Management

Track agents through their full lifecycle with administrative status and lifecycle stages:

Administrative Status: PENDING, ACTIVE, SUSPENDED, DEREGISTERED

Lifecycle Stage: EXPERIMENTAL, STABLE, DEPRECATED, RETIRED

Version History

Immutable version snapshots are created on every update to an agent’s registration. The registry supports version diffing and rollback to any previous version.

Enterprise Governance

Enterprise-grade controls including:

• Approval workflows for new agent registrations
• Registration policies and change windows
• Audit logging of all operations
• Compliance reporting
• Tenant-scoped administration with optional cross-tenant federation

Architecture

The Agent Registry follows a stateless API architecture backed by proven platform infrastructure, OIDC authentication, fine-grained authorization, event streaming, and relational storage.

Artifact Preview

Agents produce artifacts (query results, generated reports, intermediate data) that the platform can preview without forcing a full download. The Assets service exposes a preview endpoint that returns a structured snapshot of an artifact.

Defaults (effective with em-runtime 5.3+):

• Default row limit: 500 rows (raised from 10)
• Maximum byte budget: 512 KB per response (raised from 64 KB)
• Maximum row limit: 10,000 rows (cap regardless of caller request)

Response metadata (PreviewMetadata):

• size_bytes: total file size for tabular, text, and raw artifacts (always present)
• truncated: boolean flag set when either the row limit or the byte budget was reached

The service applies a byte-level truncation backstop after row-level limits, so a response that cuts cleanly at a record boundary still respects max_bytes. Callers should always check truncated before assuming a preview reflects the full artifact.

MCP Tool Integrations

The em-runtime MCP server exposes tool sets that agents can invoke via the Model Context Protocol. These tools proxy authenticated calls to platform services using the caller’s JWT and project context.

Talk2Data Tools

When TALK2DATA_BASE_URL is configured, the following tools are available:

Tool	Description
generate_sql_mcp	Generate SQL from a natural-language question against a specified data source and schema
execute_query_mcp	Execute a SQL query against a data connection and return results
resolve_term_mcp	Resolve a business term to its canonical definition using the data catalog
generate_plotly_chart_mcp	Generate a Plotly chart specification from query results

These tools forward requests to the Talk2Data Service using the caller’s bearer token and X-Project-ID header. If TALK2DATA_BASE_URL is not set, the tools return a talk2data_not_configured error. See Data Insights Overview for Talk2Data deployment.

Catalog Tools

The MCP server also exposes metadata and search tools against the Utils service (data catalog):

• get_schema_mcp — Get schema metadata for a data connection entity by FQN
• list_metadata_mcp — List metadata assets with filtering
• search_metadata_mcp — Full-text search across the data catalog

Webhook Events

The registry emits events after successful registration operations.

Event Category	Examples
Registration	Agent registered, updated, deregistered
Health	Health status changed, probe failed
Lifecycle	Stage transition (e.g., EXPERIMENTAL to STABLE)
Search	New agent matches a saved search filter

Well-Known URI Crawling

The registry can automatically discover agents from configured domains by crawling their /.well-known/agent-card.json endpoints:

• Scheduled crawls with configurable intervals
• Caching to minimize network traffic
• Drift detection to identify when a remote Agent Card changes
• SSRF protection for all outbound requests

Multi-Tenancy

The registry supports full multi-tenant isolation:

• Namespace isolation — each tenant’s agents are invisible to other tenants
• Tenant-scoped administration — per-tenant admin roles and policies
• Cross-tenant federation — optional sharing of selected agents across tenants
• Cost attribution — per-tenant usage metering, quota enforcement, and chargeback

Target Personas

Persona	Use Case
Agent Developer	Register, update, and manage A2A Agent Cards. Validate cards before publishing. Track health and manage versions.
MCP Server Developer	Register MCP server metadata (tools, resources, prompts). Validate tool schemas. Publish to both this registry and the MCP public registry.
Consumer	Search by skill tags, keywords, provider, capabilities, and protocol. Filter by health and verification status.
Platform Operator	Deploy and scale the registry. Monitor health, latency, and throughput. Configure health check intervals.
Enterprise Admin	Control registration policies. Configure approval workflows. Audit operations. Enforce security policies.

Success Metrics

Metric	Target
API availability	99.9% monthly
Search p99 latency	< 500ms
Registration p99 latency	< 1000ms
Search index lag	< 30 seconds
Webhook first delivery	< 60 seconds
Registered entities capacity	100K+ agents and servers
Search throughput	1K+ queries/second

Next Steps

Data Connections

Configure data source connections used by agents for data access.

Webhooks

Set up webhook notifications for agent lifecycle events.

Data Insights Agents

See how Data Insights uses A2A agents for conversational analytics.

Security Model

Understand authentication, authorization, and multi-tenant isolation.