VCN #36: Crosstalk — Build Your Own A2A Endpoint
Two agents in the room discover each other. Then the whole room does. A2A and Cotal, live, no middleman.
A2A v1.0.0 shipped under Linux Foundation governance in March 2026. JSON-RPC 2.0 over HTTPS. Agent cards at /.well-known/agent-card.json declare identity, capabilities, skills, and security schemes. 150+ organizations ship it: Atlassian, Box, Cohere, MongoDB, PayPal, Salesforce, SAP, ServiceNow, Workday.
And almost nobody at a meetup has actually shipped one. VCN #36: Crosstalk changes that in one night, in two parts.
Part 1: Crosstalk, the handshake. Every builder in the room runs a tiny A2A server with one skill. A mini registry, built live, scrapes every agent card in the room. Then we let agents find each other. One calls another. Logs print. Receipts visible.
A 30 line A2A server. Python SDK (
pip install a2a-sdk). Pick one skill you already have a function for: summarize a URL, look up a calendar event, translate a string.The agent card. Hand written
/.well-known/agent-card.json. Identity, one skill, security scheme.The mini registry. Two laptop demo first, then we open it to the room.
GetExtendedAgentCard. Same card, two views, gated by an auth header. The capability disclosure pattern.
Part 2: Cotal, from one to many. A2A is the handshake between two agents. Cotal is the web for agents: one protocol where agents meet as peers, broadcast, DM, and route by role, with no orchestrator in the middle. Cotal is a startup building here at the tower, and they take the room from a single handshake to a whole mesh of agents talking at once.
By 10pm your agent has handshook with a stranger's agent and joined a room full of them. You leave with a 50 line A2A server you wrote, a working mini registry pattern, and a clear read on where one to one ends and one to many begins.
Builders only. Laptop required. Bring an agent, any agent, any framework.
Doors 7pm. Talks 7:30. Frontier Tower, 10th Floor Annex, 995 Market Street.
Hosted by Vibe Coding Nights: Rayyan Zahid (Immersive Commons), Michalis Vasileiadis (Otto / GSD2.0), Eric Mockler (F11 Health & Longevity), Devinder Sodhi (Tower Lead, Frontier Tower). Part 2 by the Cotal team.
RSVP if you want your agent talking to other agents.