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 instructions/mark3labs/mcphost/agents-mdgit clone --depth 1 https://github.com/mark3labs/mcphostWhat 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 | $0.00380 | $0.00380 |
| Opus 5 | $0.00190 | $0.00190 |
| Sonnet 5 | $0.00076 | $0.00076 |
| Haiku 4.5 | $0.00038 | $0.00038 |
Grade A, and why
mcphost AGENTS.md 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.
What it actually says
OpenSpec Instructions
These instructions are for AI assistants working in this project.
Always open @/openspec/AGENTS.md when the request:
- Mentions planning or proposals (words like proposal, spec, change, plan)
- Introduces new capabilities, breaking changes, architecture shifts, or big performance/security work
- Sounds ambiguous and you need the authoritative spec before coding
Use @/openspec/AGENTS.md to learn:
- How to create and apply change proposals
- Spec format and conventions
- Project structure and guidelines
Keep this managed block so 'openspec update' can refresh the instructions.
MCPHost Agent Guidelines
Build/Test Commands
- Build:
go build -o output/mcphost - Test all:
go test -race ./... - Test single:
go test -race ./cmd -run TestScriptExecution - Lint:
go vet ./... - Format:
go fmt ./...
Code Style
- Imports: stdlib → third-party → local (blank lines between)
- Naming: camelCase (unexported), PascalCase (exported)
- Errors: Always check, wrap with
fmt.Errorf("context: %w", err) - Logging: Use
github.com/charmbracelet/logstructured logging - Types: Prefer
anyoverinterface{} - JSON: snake_case tags with
omitemptywhere appropriate - Context: First parameter for blocking operations
Architecture
- Multi-provider LLM support via
llm.Providerinterface - MCP client-server for tool integration
- Builtin servers: bash, fetch, todo, fs
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.
- 2d ago First seen · 41 lines · 380 tokens per session scan A 70c579aef2ea
mcphost AGENTS.md is an instructions file published in the GitHub repository mark3labs/mcphost (1,597 stars, last pushed 4mo ago), licensed MIT. It adds 380 tokens to every session, about $0.0019 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.
Other instructions, from other repositories
vscode buildNext.instructions.md
Working notes and architecture documentation for the new esbuild-based build system in build/next. Use when making changes to the new build pipeline (transpile/bundle commands, NLS plugin, source-map handling, resource copying, or self-hosting watch tasks).
spec-kit AGENTS.md
AGENTS.md instructions for github/spec-kit, covering agents.md, about spec kit and specify, quickstart — add a new integration in 5 steps, integration architecture and integrationmanifest — file tracking.
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langchain AGENTS.md
AGENTS.md instructions for langchain-ai/langchain, covering global development guidelines for the langchain monorepo, corridor security analysis, project architecture and context, monorepo structure and development tools & commands.
vscode oss-third-party-notices.instructions.md
Instructions for microsoft/vscode, covering vs code oss third-party-notices pipeline, architecture, pipeline flow in ci, applying the notice (cutover) and fallback chain (never fail the build).
next.js AGENTS.md
Instructions for vercel/next.js, covering next.js development guide, codebase structure, monorepo overview, core package: packages/next and other important packages.