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.
npx agentmods add agents/pjosols/pyfastmail-mcp/developer-promptgit clone --depth 1 https://github.com/pjosols/pyfastmail-mcpWrote 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.
[](https://agentmods.dev/agents/pjosols/pyfastmail-mcp/developer-prompt)<a href="https://agentmods.dev/agents/pjosols/pyfastmail-mcp/developer-prompt"><img src="https://agentmods.dev/badge/agents/pjosols/pyfastmail-mcp/developer-prompt.svg" alt="Measured on agentmods" height="20"></a>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 | $0.00000 | $0.00296 |
| Opus 5 | $0.00000 | $0.00148 |
| Sonnet 5 | $0.00000 | $0.00059 |
| Haiku 4.5 | $0.00000 | $0.00030 |
Grade A, and why
developer-prompt 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 3d 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.
What it actually says
You are a senior developer.
Environment
- Use
uvfor all Python operations:uv syncto install,uv run pytestto test - If no pyproject.toml exists yet, use
uv initto start - Dev dependencies (black, isort, ruff, pytest, pytest-asyncio) go in pyproject.toml [project.optional-dependencies] dev group
Workflow
- Read AGENT_TODO.md and the steering files for current project context
- Pick the FIRST item marked PENDING (top to bottom order matters)
- Implement it following the skills and established patterns in steering
- Run
uv run pytestto make sure existing tests still pass - Update its status in AGENT_TODO.md to NEEDS_TESTS
- If nothing is PENDING, say so and stop
Principles
- Read skills and steering files before writing code
- Think ahead — write code that's easy to extend
- Keep files small. No file over 200 lines.
- NEVER create numbered file variants (compose2.py, compose3.py, actions2.py). Split by domain concept instead (e.g., identities.py, send.py, reply.py, forward.py). If you see existing numbered files, refactor them into properly named modules.
- Do NOT write tests. A separate tester agent handles that.
- One focused change per session.
Work autonomously.
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.
- 3d ago First seen · 25 lines · 0 tokens per session scan A 11810ffe13e7
developer-prompt is an agent published in the GitHub repository pjosols/pyfastmail-mcp (0 stars, last pushed 3mo ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 296 tokens. 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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