Let Other Agents Call Yours

In this tutorial you make your agent reachable by other agents. You will turn on Agent-to-Agent, fill in your agent's card so other agents know what to ask it, choose which tools they may use, and create a key for each agent you let in.

Before you start

• Read Work With Other Agents to understand the outbound and inbound directions.
• Your agent answers its specialist questions well in Preview. Other agents will rely on those answers.
• You know how to publish changes. See Preview and Publish Changes.
• You have Owner or Contributor access to the agent.

This tutorial is done on Ledger, Kirana Group's finance assistant. Ledger answers questions about vendor payments from Kirana's payment rules:

• Standard terms are Net 30 from receipt of a complete invoice.
• Payment runs happen every Tuesday and Friday.
• An invoice needs the purchase order number, a signed delivery note or service acceptance, and the vendor's Faktur Pajak (tax invoice).
• Invoices above USD 50,000 also need Finance Controller sign-off.

Kirana's operations assistant Atlas should be able to ask Ledger these questions. You open Ledger for Atlas here; on Atlas, you then connect Ledger in Call Other Agents.

Step 1: Turn on Agent-to-Agent

1. In Ledger's left sidebar, open Channels → Agent-to-Agent. A blue box reads This is the inbound direction.
2. Switch on Reachable by other agents.

The switch is off by default. It is separate from making your chat page public: other agents connect through a secure link, not through your public chat page. The rest of the page only appears once the switch is on.

Step 2: Copy the share link

Under Share Ledger you see Ledger's link with a copy button:

https://api.qlar.ai/dialog/a2a/ledger-finance/card

This is the link you give to whoever wants to connect their agent. They also need a key from you, which you create under Manage API keys (Step 6). If the page says "Save this agent first to get its link.", save the page first.

The note under the link says it plainly: "The link starts working once Ledger is published." You publish in Step 7.

Step 3: Fill in the agent card

The Agent card tab (heading Configure Ledger's Agent Card) describes your agent to other agents, like a business card: who it is, what it is good at, and how to reach it.

You can let qlar draft it for you: click Auto-fill with AI, or click Add suggestions in the banner "We can suggest questions, topics, and a description from Ledger's profile." Dismiss hides the banner. Review and edit what it fills in.

Add at least one example question. Without one, a warning appears on the tab and other agents cannot find your agent. The counter next to the label shows how many you have, for example · 2 questions.

Write the description for the agent that will call you. Atlas reads it when it decides whether a question belongs to Ledger, so name the topics Ledger covers.

Open Advanced technical details to see the protocol (A2A, JSON-RPC 2.0), the endpoint, and the current limits: your agent replies in text only, one complete reply per request, and it can pause to ask the calling agent a question when it needs more information.

Step 4: Choose which tools callers may use

Open the Tool access tab.

Other agents can always ask your agent questions. Everything else is off until you allow it. Turn on only what you would be comfortable with another team's agent using.

Ledger answers from its knowledge and has no tools, so the tab only says: "Ledger has no tools yet. When you add tools, you can choose which ones other agents may use here." There is nothing to switch on. Atlas can still ask Ledger questions.

When your agent has tools, the tab lists them and the header shows how many are allowed, for example 1 of 4 allowed:

1. Use Search tools or the All, Allowed and Not allowed filters to find a tool.
2. Switch on each tool callers may use. Tools are grouped as Built-in (for example Web search), Your custom tools, MCP tools and Plugins.

A fixed section at the bottom lists tools you cannot change. The Knowledge base is always on (read-only). Hand over to a person and tools that call other agents can never be allowed, so a caller cannot reach your supervisors or chain through to your other agents.

Example: suppose Finance later gives Ledger a read-only API that looks up an invoice's payment status, and another API that schedules a payment. Allow only the lookup. Atlas can then tell a project manager where an invoice stands, but can never schedule a payment.

Step 5: Save

Click Save all changes at the bottom of the page and confirm.

Step 6: Create a key for Atlas

Every agent that connects needs a key from you. No key, no entry.

1. Open Channels → Agent Keys. The Agent-to-Agent page links to it under Manage API keys.
2. Under Make a key for another agent, fill in both boxes:
   • Who is this key for?: name it after the caller. For Ledger, enter Atlas (Kirana operations).
   • How long should it work?: 7, 14, 30, 90 or 365 days. Choose 365 days. The key stops working on its own when the time is up.
3. Click Create key. The CMS asks Are you sure to add this agent key? Confirm.
4. The new key opens in the Keys you've handed out list, marked Active and Expires in 1 year. Copy the Main key and send it, together with the share link from Step 2, to Atlas's owner.

Each key entry has two values: a Main key to hand out and a Backup key to keep ready, so you can swap keys without downtime. In each entry you can also:

Step 7: Publish

Click Publish at the top of the CMS. Ledger's share link only starts working once Ledger is published, and other agents always talk to the published version.

Agent Keys and the classic protocol

The keys on Channels → Agent Keys serve two kinds of callers:

• A2A callers, as described above. A turned-off or expired key is refused.
• Classic callers, which use the older key-based connection: another agent's owner enters your agent's code and one of your keys under Classic connections (manual key) on their Tools → Other Agents page.

The classic protocol is pending sunset. When it is retired, the Agent Keys page will merge into Agent-to-Agent. Until then, keep the keys of any classic callers in place, and give new callers the share link plus a key so they connect over A2A.

Check the result

1. On Atlas, connect Ledger with the share link and key, as described in Call Other Agents.
2. In Atlas's Preview, ask "When will Finance pay a vendor invoice?". Atlas should get the answer from Ledger: Net 30 from receipt of a complete invoice, in the Tuesday or Friday payment run.
3. On Ledger's Agent Keys page, click Turn off for the key "Atlas (Kirana operations)" and ask again. Atlas should no longer reach Ledger. Click Turn back on when you are done.

Next steps

• Next in the journey: Teach Your Agent Skills, to give your agent written procedures for specific situations.
• Call Other Agents: the outbound direction, done on Atlas.
• Reference: Agent-to-Agent and Agent Keys.