Borrowing it
Nothing to install: this file belongs to conorbronsdon/substack-mcp. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/conorbronsdon/substack-mcp/main/CLAUDE.mdgit clone --depth 1 https://github.com/conorbronsdon/substack-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/instructions/conorbronsdon/substack-mcp/claude-md)<a href="https://agentmods.dev/instructions/conorbronsdon/substack-mcp/claude-md"><img src="https://agentmods.dev/badge/instructions/conorbronsdon/substack-mcp/claude-md/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.
<a href="https://agentmods.dev/instructions/conorbronsdon/substack-mcp/claude-md"><img src="https://agentmods.dev/badge/instructions/conorbronsdon/substack-mcp/claude-md.svg" alt="Reviewed on agentmods" width="80" 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 5.1 | $0.00803 | $0.00803 |
| Opus 5.5 | $0.00321 | $0.00321 |
| Sonnet 5.5 | $0.00161 | $0.00161 |
| Haiku 4.5 | $0.00080 | $0.00080 |
Grade A, and why
substack-mcp CLAUDE.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 today.
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.
How it starts
The opening of the file, as written. The whole thing — 45 lines — stays where its author put it; the contents beside it link to each section on GitHub.
substack-mcp
MCP server for Substack — read posts, manage drafts, create notes. Cannot publish or delete posts by design; notes (short-form) publish immediately since Substack has no note-draft state.
Architecture
src/index.ts— MCP server bootstrap and entry point; picks stdio (default) or HTTP transport viaMCP_TRANSPORTsrc/transport/http.ts— Stateless Streamable HTTP transport (POST /mcp,GET /health) for persistent/networked deploymentssrc/server.ts— Tool registration, request handlers, Zod schema generation;createServer(publications: PublicationConfig[])takes one client per configured publicationsrc/annotations.ts— Tool side-effect classification (read / draft-write / public-upload / publish) → MCP annotations (hints set explicitly; MCP defaults omitted hints to the unsafe direction)src/auth/resolve-credentials.ts— Single-publication env-var + stored-session credential resolution (the original, still-supported contract)src/auth/resolve-publications.ts— Multi-publication credential resolution (SUBSTACK_PUB_<KEY>_*env vars), falling back toresolve-credentials.tswhen none are setsrc/api/client.ts— HTTP client for Substack API (session cookie auth)src/api/types.ts— TypeScript interfaces for API responsessrc/utils/errors.ts— Error handling utilitiessrc/utils/markdown-to-prosemirror.ts— Markdown to ProseMirror AST converter (Substack editor format)src/__tests__/— Vitest tests for client, errors, and markdown conversion
Key constraints
- Posts are read/draft only — no publish or delete capabilities by design
- Notes publish immediately via
create_note/create_note_with_link— Substack has no note-draft state, so there is no preview step - Auth sends both
connect.sidandsubstack.sidcookies set to the same session token (custom domains use their ownconnect.sid; substack.com'ssubstack.sidis a different session rejected by a custom domain) - Markdown must be converted to ProseMirror format for Substack's editor
- Community writes: see
docs/community-writes.md. Comments use the selected publication; restacks use a separately configured reader session and explicit account ID. Both preview by default, require exact per-call consent, and are disabled for live writes unless explicitly enabled. - With 2+ publications configured (
SUBSTACK_PUB_<KEY>_*), every publication tool gains a requiredpublicationenum parameter — no default, no guessing. With exactly one publication configured, nopublicationparameter is added at all (schema-identical to single-publication mode)
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.
- today Changed · +1 lines · +53 tokens per session 8c5620beda8d
- 25d ago Changed · +11 tokens per session 86ebee642082
- 1mo ago Changed · -1 lines · -4 tokens per session d0c1d00decf9
- 1mo ago Changed a2af91e2609d
- 1mo ago Changed · +4 lines · +198 tokens per session 40d4cea68532
- 1mo ago First seen · 41 lines · 545 tokens per session scan A cc8291f01ccf
substack-mcp CLAUDE.md is an instructions file published in the GitHub repository conorbronsdon/substack-mcp (44 stars, last pushed yesterday), licensed MIT. It adds 803 tokens to every session, about $0.0032 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 2026-08-30.
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).
next.js AGENTS.md
AGENTS.md instructions for vercel/next.js, covering next.js development guide, codebase structure, monorepo overview, core package: packages/next and other important packages.
vscode oss-third-party-notices.instructions.md
Instructions for microsoft/vscode, covering vs code oss third-party-notices pipeline, architecture, pipeline flow in ci, cache eligibility and rollout and applying the notice (cutover).
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 copilot-instructions.md
Copilot instructions for microsoft/vscode, covering vs code copilot instructions, project overview, root folders, core architecture (src/ folder) and built-in extensions (extensions/ folder).
vscode model-prompts.instructions.md
Model-specific prompt authoring and registry guidelines.