What is matrix-openapi-skill?

A connection to Matrix, an open messaging system where conversations are hosted on independent servers called homeservers. It can read account, room, profile, presence, and sync data, and send room messages.

Use it to find joined rooms, inspect room state, poll for new events, look up users, check presence, and send messages.

It provides a consistent way to work with Matrix rooms and messages once an access token and homeserver are available. It does not handle login, account setup, or the full Matrix specification.

matrix-openapi-skill — Skill for Codex by holon-run/uxc

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent

npx skills add holon-run/uxc --skill matrix-openapi-skill

Clone the repo

git clone --depth 1 https://github.com/holon-run/uxc

Made for: Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/skills/holon-run/uxc/matrix-openapi-skill/github.svg)](https://agentmods.dev/skills/holon-run/uxc/matrix-openapi-skill)

Your own site

<a href="https://agentmods.dev/skills/holon-run/uxc/matrix-openapi-skill"><img src="https://agentmods.dev/badge/skills/holon-run/uxc/matrix-openapi-skill/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/skills/holon-run/uxc/matrix-openapi-skill"><img src="https://agentmods.dev/badge/skills/holon-run/uxc/matrix-openapi-skill.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 34 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 1,635 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits

NVIDIA SkillSpector warn 7 Sept 2026

SkillSpector: 2 findings, up to high

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

high Privilege Escalation · line 18
Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.

Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
high Privilege Escalation · line 72
Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.

Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.

How audits are shown

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.00034	$0.01635
Opus 5.5	$0.00014	$0.00654
Sonnet 5.5	$0.00007	$0.00327
Haiku 4.5	$0.00003	$0.00163

Measured 1mo ago against content hash 2fb2d5969d67, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

matrix-openapi-skill scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/validate.sh), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/matrix-openapi-skill/SKILL.md · 165 lines

How it starts

The opening of the file, as written. The whole thing — 165 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Matrix Client-Server API Skill

Use this skill to run Matrix Client-Server operations through uxc + OpenAPI.

Reuse the uxc skill for shared execution, auth, and error-handling guidance.

Prerequisites

uxc is installed and available in PATH.
Network access to your Matrix homeserver's client-server base URL, usually https://<homeserver>/_matrix/client/v3.
Access to the curated OpenAPI schema URL:
- https://raw.githubusercontent.com/holon-run/uxc/main/skills/matrix-openapi-skill/references/matrix-client-server.openapi.json
A Matrix access token for the target homeserver.

Scope

This skill covers a practical request/response Matrix surface:

token owner lookup
joined room discovery
room state lookup
/sync polling reads, including daemon-backed poll subscribe
user profile and presence lookup
room message sends

This skill does not cover:

login, SSO, device registration, or generic token acquisition flows
appservice, federation, or bot framework abstractions
webhook or long-running event receiver runtime
full Matrix spec coverage

Homeserver Base URL

Matrix is homeserver-specific. The endpoint you link must include the Matrix client-server base path:

typical form: https://<homeserver>/_matrix/client/v3
example form: https://matrix.org/_matrix/client/v3

Do not link only the homeserver origin without /_matrix/client/v3.

Authentication

Matrix Client-Server API uses Authorization: Bearer <access_token>.

Preferred path for OAuth-aware homeservers:

uxc auth oauth start matrix-oauth \
  --endpoint https://matrix.org/_matrix/client/v3 \
  --redirect-uri http://127.0.0.1:8788/callback \
  --client-id <client_id>

uxc auth oauth complete matrix-oauth \
  --session-id <session_id> \
  --authorization-response 'http://127.0.0.1:8788/callback?code=...'

uxc auth binding add \
  --id matrix-oauth \
  --host matrix.org \
  --path-prefix /_matrix/client/v3 \
  --scheme https \
  --credential matrix-oauth \
  --priority 100

Read the full file on GitHub · 165 lines

Files

What ships with it

4 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

1mo ago First seen · 165 lines · 34 tokens per session scan A 2fb2d5969d67

Subscribe to this mod's changes

matrix-openapi-skill is a skill published in the GitHub repository holon-run/uxc (119 stars, last pushed 1mo ago), licensed MIT. It adds 34 tokens to every session and 1,635 once invoked, about $0.0001 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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