agent-api-guide

Agent Building

Guide for the inter-host agent API system. Use when adding capabilities to hosts, writing handlers, understanding the GC protocol, or debugging agent call issues.

QUICK START

How to use this skill

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Review the proposed files and risks before you approve installation.

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I want to install this Agent Skill for this project in Codex.

Source SKILL.md: https://github.com/majiayu000/claude-skill-registry/blob/HEAD/skills/development/agent-api-guide/SKILL.md

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Agent API Guide

This skill covers the fort-agent system for secure inter-host communication. Hosts can expose capabilities that other hosts call via signed HTTP requests.

Quick Reference

Client (calling a capability):

fort-agent-call <host> <capability> [request-json]

Provider (exposing a capability):

fort.capabilities.my-capability = {
  handler = ./handlers/my-capability;  # Script that handles requests
  needsGC = false;                      # Enable garbage collection
  ttl = 0;                              # GC time-to-live in seconds
  description = "What this does";
};

Consumer (depending on a capability):

fort.needs.my-capability.my-id = {
  providers = ["hostname"];             # Host(s) providing this
  request = { key = "value"; };         # Request payload
  store = "/var/lib/myapp/response";    # Where to store response
  restart = ["myapp.service"];          # Services to restart on change
};

Key Files

Path	Purpose
`common/fort-agent.nix`	Nix module defining options and config generation
`pkgs/fort-agent-call/`	Client script (Bash)
`pkgs/fort-agent-wrapper/`	Server (Go FastCGI)
`/etc/fort-agent/`	Runtime config on hosts
`/var/lib/fort-agent/`	GC handles and state

Detailed Documentation

capabilities.md - Adding capabilities to hosts
handlers.md - Writing handler scripts
gc-protocol.md - Garbage collection system
troubleshooting.md - Debugging issues

Standard Capabilities

All hosts expose these capabilities:

Capability	Returns
`status`	Hostname, uptime, failed units, deploy info
`manifest`	Apps, aspects, roles, exposed services
`holdings`	GC handles currently in use

Authentication & RBAC

Requests signed with SSH keys (ssh-keygen -Y sign)
RBAC computed at eval time from cluster topology
Only hosts that fort.needs a capability can call it
Config files: /etc/fort-agent/hosts.json, /etc/fort-agent/rbac.json