aciapi(a4i)

CLI/MCP/Python Library for the Cisco ACI REST API.

• The token is never written to disk. login hands it to a small per-user daemon that holds it in memory, behind a Unix domain socket, so it survives across short-lived CLI invocations without touching the filesystem.

• The ACI object model ships with it. search and describe answer what a class is called and what a body may set on it, without an APIC and without a login.

• merge and diff compare a fabric against an intended configuration, reporting both what the configuration asks for and the fabric lacks, and what the fabric carries and the configuration never mentions.

• plan posts only what changes. It narrows a configuration to the MOs a POST of it would actually change, so the MOs the fabric already agrees with are never handed back to the APIC to be written again.

Install

pip install a4i

Shell completion is printed to standard output; add one line to your shell's startup file:

eval "$(a4i generate-shell-completion zsh)"    # ~/.zshrc, after compinit
eval "$(a4i generate-shell-completion bash)"   # ~/.bashrc
a4i generate-shell-completion fish | source    # ~/.config/fish/config.fish

Related MCP server: quads-mcp

Usage

a4i login apic1.example.com -u admin              # prompts for password; -k if self-signed
a4i get class fvTenant                            # class query
a4i get mo uni/tn-common                          # MO query, by DN
a4i get class fvTenant --query-target subtree --rsp-subtree full
a4i get class l1PhysIf --node leaf101.example.com # query a switch with the same token
echo '{"fvTenant":{"attributes":{"name":"demo"}}}' | a4i post mo uni/tn-demo
a4i logout                                        # drop the in-memory session
a4i daemon status                                 # is a token held, and for how long
a4i login apic1.example.com -u admin --read-only  # a session that will refuse every POST
a4i mcp                                           # serve MCP on stdio for an LLM client

get, post and list each take a class or an mo subcommand, so a DN needs no leading / and a class name is never mistaken for one. Every get option is named after the ACI query parameter it sets, so a parameter read in the APIC REST API documentation can be typed as-is -- a4i get class --help lists them.

Reading the model

a4i search 'bridge domain'          # which class is that, by name
a4i describe fvBD                   # what a body may set on it
a4i list class fvT                  # class names starting with fvT
a4i list mo uni/tn-common           # the MOs one level under that DN

search, describe and list class read the bundled dictionary, so they need neither a login nor a daemon. list mo asks the APIC for one level of children, so it needs a session.

$ a4i describe fvCtx
fvCtx  VRF
The private layer 3 network context that belongs to a specific tenant or is
shared.

rn  ctx-{name}
dn  uni/tn-{name}/ctx-{name}
in  fvTenant

properties (13 settable, 14 read-only hidden)
  descr                string:Basic (0-128)            Specifies a descriptio…
  ipDataPlaneLearning  disabled|enabled = enabled
  name*                string:Basic (1-64)             A name for the network…
  pcEnfDir             egress|ingress|mixed = ingress  Policy Control Enforce…
  pcEnfPref            enforced|unenforced = enforced
  …
children (42)  --children to list them

A * marks a naming property -- the one the RN is built from. The middle column is what the property accepts, with the default after =. -a spells out the read-only properties, --children the classes that may hang under this one, and --json prints the underlying record instead of the layout.

Comparing a configuration

merge folds a configuration written across several files into the one body that diff and post each take, later files winning attribute by attribute. Two files mean the same MO when they resolve to the same DN, however each one said so. The result is a polUni holding every merged MO nested under the MO it hangs off, which is the shape a POST to uni takes; diff compares that same body against everything the fabric has under uni.

a4i merge ./configs/ -o merged.json               # every *.json, in path order
a4i merge ./configs/ | a4i post mo uni --dry-run  # what posting it would change
a4i merge ./configs/ | a4i post mo uni
a4i merge ./configs/ | a4i diff
a4i merge ./configs/ | a4i diff --exclude uni/tn-common --exclude uni/infra
a4i post mo uni/tn-demo --dry-run '{"fvTenant":{"attributes":{"descr":"prod"}}}'

plan narrows that same configuration to the MOs posting it would change, and writes them out as a body of their own. Posting the whole configuration hands the APIC every MO it already agrees with, and the APIC writes all of them; posting a plan writes what the report named and nothing else. The report goes to standard error and the body to standard output, both from one read of the fabric.

a4i merge ./configs/ | a4i plan            # report on stderr, body on stdout
a4i plan merged.json -o plan.json          # -o and --force, as merge takes them
a4i plan merged.json -o plan.json && a4i post mo uni plan.json

The body is shaped exactly as a merged one is, so the two can be read side by side. An MO that changes carries the attributes that change and a status saying what the fabric was just found to be -- so a fabric that has moved on refuses the POST rather than doing something nobody read. The MOs the report has no line for are there to nest what does change under them, and carry rn and status="modified" only.

Every DN on the way down from uni has to be described by something: a BD written without its tenant is refused rather than nested under a tenant merge made up, and an MO whose DN does not sit under uni is refused too -- post that one on its own. --loose fills the missing ancestor in instead, where the bundled dictionary settles what class sits there.

- fvTenant uni/tn-common  (extra: 2 child MOs)
  - descr: ""
  - name: "common"

~ fvBD uni/tn-demo/BD-bd1
  ~ mtu: "1500" -> "9000"

+ fvTenant uni/tn-new  (missing: 2 child MOs)
  + descr: "added"
  + name: "new"

1 missing, 1 modified, 1 extra

+ is an MO the configuration asks for and the fabric does not have, - one the fabric has and the configuration does not mention, and ~ one whose attributes differ. A wholly missing or wholly extra subtree is reported as its top MO with the MOs below it counted; --expand lists every one of them.

The configuration is taken to describe the whole of uni, so everything it leaves out is extra -- including tn-common, tn-infra, tn-mgmt and the policies the APIC creates for itself. --exclude is how the rest is quietened: it takes a DN, or a pattern whose * matches within one RN, and is repeatable.

post --dry-run reads the same way over a single POST: it fetches the subtree the body targets, prints what would change, and sends nothing. Both commands say in their exit code whether anything would change:

MCP server

a4i mcp speaks the Model Context Protocol on stdin and stdout, so an LLM client can read and write the fabric through the session you already logged in. Register it with the client, then log in from a terminal as usual -- there is no login tool, because this server never handles a password.

{"mcpServers": {"a4i": {"command": "a4i", "args": ["mcp"]}}}

A get whose response would exceed 64 KB is refused, with the total count and the ways to narrow it; A4I_MCP_MAX_BYTES raises or lowers that. On a --read-only session, post is not offered at all.

Python library

A Client holds its own session, so no daemon is involved: it logs in itself and keeps the token in memory for as long as it lives.

import a4i
from a4i.merge import merge

with a4i.Client("apic1.example.com", verify=False) as client:
    client.login("admin", password)

    data = client.get("fvTenant", kind="class", query_target="subtree", rsp_subtree="full")
    client.post("uni/tn-demo", {"fvTenant": {"attributes": {"name": "demo"}}}, kind="mo")
    changes = client.diff(merge(base, override))
    client.post("uni", client.plan(merge(base, override)).body, kind="mo")

kind is the subcommand the CLI takes, and it is required: "class" for a class name, "mo" for a DN. Every other keyword argument is the CLI option of the same name with underscores. verify is what -k/--insecure and --ca express, timeout is login --timeout, and dry_run(), diff(), plan() and a4i.merge.merge() are the commands of those names.

AsyncClient is Client awaited: the same arguments, the same return values and the same exceptions, sending the same requests in the same order.

async with a4i.AsyncClient("apic1.example.com", verify=False) as client:
    await client.login("admin", password)
    data = await client.get("fvTenant", kind="class")

A value ACI does not define raises ValueError before anything is sent. A failed request raises a4i.ApicError, a4i.NotLoggedInError or a4i.SessionExpiredError, all of them a4i.A4iError. The token refreshes itself once half its lifetime has elapsed, so a long-running script needs nothing of its own.