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Tools are declarative. You add what the agent can call with telnyx-acp add tool, which writes it to agent.json, and the platform handles invocation, credentials and results. Web Search and MCP Servers are available today. The rest are on the roadmap, in preview.
  • Web Search: Search the live web, read a page, or research a question across sources. No key to add.
  • MCP Servers: Connect to any remote Model Context Protocol server by URL. This is the simple case, a server and an optional credential. For governed access, use Gateway.
telnyx-acp tools lists the names the model sees. A call whose execution fails returns to the model as text it can act on, not as a failed run; arguments that fail the tool’s schema still fail the run. The list can live in its own file: telnyx-acp tools --file tools.json moves it out of agent.json, which then says "tools": "tools.json", and every verb reads and writes it there. tools has the flags.

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Approvals

An approval makes a tool’s calls wait for a human. Mark the tool by the name the model sees, which telnyx-acp tools lists. A running dev reloads it.
Beta. Approvals work under telnyx-acp dev today. On a deployed agent a run with an ask tool pauses, but the platform does not yet keep the approval to decide, so the run cannot be approved and fails after 15 minutes; deploy warns when agent.json has an ask entry. Keep ask out of a deployed agent until that lands.
A run that reaches fetch_page pauses. Under telnyx-acp dev, invoke --local ends with the approval’s id instead of a reply.
Approve or deny it within 15 minutes, by that id.
Tools that are not named run without asking (allow); deny hides a tool from the model. telnyx-acp unset approvals.fetch_page removes the entry.

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Limits

limits.steps caps the model steps one run may take, 8 by default. A step is one model generation, with whatever tool calls it requests; the generation that reads their results is the next step. On a call, tools run only with voice.harness on, and a tool marked ask is left out even then, since a call cannot wait for an approval; the agent says so once in the logs, {"voiceTools":"left out on calls","tools":[…],"reason":"a call cannot wait for an approval"}. Texts and invoke keep the full set. Limits, Approvals, Tools has the agent.json fields.

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On the Roadmap

These tools are in preview. An agent cannot call them yet.
  • Gateway Preview Governed connectivity to APIs and MCP servers, with authentication, access control and policy. Reference an instance and every tool configured on it becomes available.
  • Browser Preview Managed web browsing and automation.
  • Sandbox Preview Sandboxed code execution for data analysis and computation.
  • File System Preview View, create and edit files on a CloudFS mount.