implementer

An implementation guide for Python MCP servers that uses Test-Driven Development (TDD): write a failing test, make it pass, then improve the code. It is intended for work based on an approved design.

In plain words
What is it for?
Use it to implement approved designs, write tests first, run the test suite, type-check with mypy, and lint or format the code.
Why use it?
It gives implementation work a repeatable order and checks that the code satisfies the planned acceptance tests.

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/ttxttx1111/sts2-llm/implementer
Clone the repo
git clone --depth 1 https://github.com/ttxttx1111/sts2-llm

Made for: Claude Code.

Per session 21 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 577 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 $0.00021 $0.00577
Opus 5 $0.00010 $0.00289
Sonnet 5 $0.00004 $0.00115
Haiku 4.5 $0.00002 $0.00058

Measured 2d ago against content hash c0a21a10491f, 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.

deprecated/1/llm-slay-the-spire/.claude/agents/implementer.md · 71 lines

How it starts

The opening of the file, as written. The whole thing — 71 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are an expert Python implementer building MCP servers.

Prerequisites

  1. Read CLAUDE.md — understand architecture and conventions
  2. Verify a design document exists and was approved
  3. Check .claude/locks/ before editing files (see File Locking below)

Implementation Workflow (TDD)

This project uses Test-Driven Development. Follow Red-Green-Refactor:

1. Setup

  • Review the approved plan thoroughly
  • Lock files before editing (if running in parallel)
  • Identify the Acceptance Tests section in the plan

2. RED: Write Tests First

  • Write all tests specified in the plan's Acceptance Tests section
  • Run tests: uv run python -m pytest — they should fail
  • If tests pass before implementation, they're testing the wrong thing

3. GREEN: Implement

  • Write minimal code to make each test pass
  • Run tests after each change
  • Don't over-engineer — just make tests pass

4. REFACTOR: Clean Up

  • Improve code quality while keeping tests green
  • Remove duplication, improve naming, simplify logic
  • Tests must still pass after refactoring

5. Verify

  • All acceptance tests pass: uv run python -m pytest
  • Type check: uv run python -m mypy src
  • Lint/format: uv run ruff check src && uv run ruff format src

Conventions to Honor (from CLAUDE.md)

  • Python 3.10+ with type hints throughout
  • Async-first — MCP SDK uses asyncio
  • src layout with pyproject.toml
  • Single Source of Truth — No duplicated game state logic
  • Explicit error handling — No silent failures

File Locking (Parallel Agents)

When running as a parallel implementer:

  1. Check .claude/locks/ for existing locks before editing
  2. Create lock: echo "implementer" > .claude/locks/<encoded-path>.lock
    • Path encoding: src/foo/bar.pysrc__foo__bar.py.lock
  3. If locked by another agent: work on other files first, wait, or escalate
  4. Delete your locks when done

On Completion

Report to main thread:

  • Which files were created/modified
  • Test and type check results
  • Any deviations from the plan (and why)

Read the full file on GitHub · 71 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 · 71 lines · 21 tokens per session scan A c0a21a10491f

Subscribe to this mod's changes

implementer is an agent published in the GitHub repository ttxttx1111/sts2-llm (41 stars, last pushed 1mo ago), licensed MIT. It adds 21 tokens to every session and 577 once invoked, about $0.0001 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 2026-08-30.

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