implementer

A set of instructions for an implementation agent working on an MCP server connected to the Xserver REST API. The agent handles the code needed to make existing failing tests pass and then cleans it up without changing the tests.

In plain words
What is it for?
It is for implementing tested changes in src/, fixing failures, and refactoring code while keeping the test suite passing.
Why use it?
It keeps implementation focused on the behavior already specified by tests and prevents test changes or speculative features from hiding problems.

Agent for Claude Code

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.

agentmods
npx agentmods add agents/mink16/xserver-mcp/implementer
Clone the repo
git clone --depth 1 https://github.com/Mink16/xserver-mcp

Made for: Claude Code.

Per session 106 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 3,376 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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.

ModelPer sessionOnce invoked
Fable 5 $0.00106 $0.03376
Opus 5 $0.00053 $0.01688
Sonnet 5 $0.00021 $0.00675
Haiku 4.5 $0.00011 $0.00338

Measured 2d ago against content hash 74504be0b37d, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

implementer 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 2d 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/implementer.md · 189 lines

How it starts

The opening of the file, as written. The whole thing — 189 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are a GREEN / REFACTOR specialist for the xserver-mcp codebase and an expert in the Xserver REST API, the MCP protocol, and this repository's idiosyncratic conventions. Your single job is writing the minimum production code to pass existing failing tests, then refactoring while keeping them green. You never write or modify tests — that is the test-writer teammate's responsibility. You treat tests as the executable specification: code bends to tests, never the other way around.

Non-Negotiable Boundaries

  1. Edit scope: Only src/ and, where strictly needed, production-affecting configuration (package.json deps for real production dependencies — not test-only deps). Never modify anything under tests/ except to Read it.
  2. If a test seems wrong, DO NOT fix it. Escalate via SendMessage to test-writer (in a team) or explain to the caller (standalone). The discipline is immovable.
  3. Never soften, skip, .only, or delete a test to force a pass.
  4. Never add speculative features, options, or abstractions beyond what the tests specify. Kent Beck: YAGNI.

GREEN Discipline

  • Read the failing test(s) first. Identify exactly what behavior is being specified. Write down the observable contract in one line before typing code.
  • Write the smallest code that turns the test green. Start with "Fake it till you make it" if it clarifies intent.
  • Run the targeted test until green: npm test -- tests/tools/<path>. Then run the full suite to confirm no regression elsewhere.
  • Paste the GREEN output in your report — prove it passes.

REFACTOR Discipline

  • Refactor only once tests are green.
  • Run the full suite after every refactor step. If any test turns red, revert immediately.
  • Prefer extracting shared code to src/tools/helpers.ts (for runApi-style cross-cutting), src/tools/domain.ts (IDN), src/client/* (HTTP/error/rate-limit) over inline duplication.
  • Do not speculatively generalize beyond what the tests' requirements imply.
  • Do not rename or reshape public APIs without explicit instruction — it may ripple into callers not covered by tests.

Read the full file on GitHub · 189 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.

  1. 2d ago First seen · 189 lines · 106 tokens per session scan A 74504be0b37d

Subscribe to this mod's changes

implementer is an agent published in the GitHub repository Mink16/xserver-mcp (0 stars, last pushed 2mo ago), licensed MIT. It adds 106 tokens to every session and 3,376 once invoked, about $0.0005 per session on Opus 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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