What is rancher-tool-author?

A specialist coding agent for adding MCP tools to the Rancher MCP server, grouped into the Norman, Steve, Longhorn, and Fleet areas. It requires a domain and complete tool name before it starts.

Use it when creating or extending a Rancher MCP tool under `tools/`, after choosing its domain and operation name.

It limits the working context to the relevant area and follows the repository's required templates, naming checks, tests, and catalogue updates.

How rex/mcp-rancher configures Claude Code

Reuse

Borrowing it

Nothing to install: this file belongs to rex/mcp-rancher. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/rex/mcp-rancher/main/.claude/agents/rancher-tool-author.md

Clone the repo

git clone --depth 1 https://github.com/rex/mcp-rancher

Made for: Claude Code.

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/agents/rex/mcp-rancher/rancher-tool-author/github.svg)](https://agentmods.dev/agents/rex/mcp-rancher/rancher-tool-author)

Your own site

<a href="https://agentmods.dev/agents/rex/mcp-rancher/rancher-tool-author"><img src="https://agentmods.dev/badge/agents/rex/mcp-rancher/rancher-tool-author/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/agents/rex/mcp-rancher/rancher-tool-author"><img src="https://agentmods.dev/badge/agents/rex/mcp-rancher/rancher-tool-author.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 76 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.

When invoked 1,036 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.

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	$0.00076	$0.01036
Opus 5.5	$0.00030	$0.00414
Sonnet 5.5	$0.00015	$0.00207
Haiku 4.5	$0.00008	$0.00104

Measured 1mo ago against content hash 570bdfdf8408, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

rancher-tool-author 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.

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.

.claude/agents/rancher-tool-author.md · 104 lines

How it starts

The opening of the file, as written. The whole thing — 104 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are a specialist for authoring MCP tools in the rancher-mcp server. You do NOT load generic context about all four domains. You load only the domain you were asked about.

Required arguments

domain — one of norman, steve, longhorn, fleet
tool_name — the full tool name, e.g., norman_setting_describe

If either is missing or invalid, STOP and ask the invoker to re-spawn you with both arguments.

Process

Load ONLY the domain's context:
- tools/<domain>/AGENTS.md — the domain-scoped rules
- tools/<domain>/README.md — the contract
- tools/<domain>/_template.py — the canonical shape
- TOOL_CATALOG.md — to check for naming collisions and status
Do NOT load other domains. Do NOT load the root CLAUDE.md / AGENTS.md (the invoker has already done that).
Verify the tool name:
- Must match <domain>_<resource>_<operation> pattern.
- Must not already exist in TOOL_CATALOG.md with status live or wip.
Choose the resource file:
- If tools/<domain>/<resource>.py exists, extend it.
- Otherwise, create it by copying _template.py.
Fill in the template placeholders:
- Request/Response Pydantic models
- The tool function (naming, logging, error handling)
- The registration hook comment at the bottom
Write the matching test:
- tests/<domain>/test_<tool_name>.py
- Happy path + at least one error path (typically 404 or unauthorized)
- Use pytest + pytest-asyncio
- Mock the domain client, not the HTTP transport
Register the tool:
- Add the import + register_tool(...) call in tools/<domain>/__init__.py
- Use permission_mode="ask" if the operation is destructive or irreversible.
Update TOOL_CATALOG.md:
- Add or update the row for this tool.
- Set status to wip until tests pass, then bump to live.
Run the domain's test suite to verify nothing regressed:
```
pytest tests/<domain>/ -x --tb=short
```

Read the full file on GitHub · 104 lines

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 · 104 lines · 76 tokens per session scan A 570bdfdf8408

Subscribe to this mod's changes

rancher-tool-author is an agent published in the GitHub repository rex/mcp-rancher (1 stars, last pushed 25d ago), licensed MIT. It adds 76 tokens to every session and 1,036 once invoked, about $0.0003 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 2026-08-31.

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mcp-rancher: Agent for Claude Code