Borrowing it
Nothing to install: this file belongs to PostHog/posthog-foss. 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/PostHog/posthog-foss/master/.agents/skills/adding-mcp-store-servers/SKILL.mdgit clone --depth 1 https://github.com/PostHog/posthog-fossWrote 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/skills/posthog/posthog-foss/adding-mcp-store-servers)<a href="https://agentmods.dev/skills/posthog/posthog-foss/adding-mcp-store-servers"><img src="https://agentmods.dev/badge/skills/posthog/posthog-foss/adding-mcp-store-servers.svg" alt="Measured on agentmods" height="20"></a>- NVIDIA SkillSpector pass
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 | $0.00107 | $0.01489 |
| Opus 5 | $0.00053 | $0.00745 |
| Sonnet 5 | $0.00021 | $0.00298 |
| Haiku 4.5 | $0.00011 | $0.00149 |
Grade A, and why
adding-mcp-store-servers 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.
How it starts
The opening of the file, as written. The whole thing — 83 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Adding a server to the MCP store
The MCP store catalog is code: one entry in products/mcp_store/backend/catalog.py per server.
On deploy, sync_mcp_server_templates upserts entries into MCPServerTemplate rows in every environment — there are no data migrations, no icon assets, and no manual admin steps for most servers.
Adding a server is a small PR to that file.
Read first
products/mcp_store/README.md— the catalog pipeline, sync semantics, and operator runbookproducts/mcp_store/backend/catalog.py— existing entries; match their tone and shapeproducts/mcp_store/backend/probe.py— what the probe verifies and whatpassed_activation_gatemeans
Workflow
-
Find the vendor's remote MCP endpoint. Check the vendor's docs (search " MCP server"); most publish a hosted endpoint like
https://mcp.<vendor>.com/mcp. Only hosted (remote) MCP servers belong in the catalog — local/stdio servers do not. Cross-check public MCP registries if the docs are unclear. -
Probe it.
DEBUG=1 python manage.py probe_mcp_server https://mcp.example.com/mcpThe JSON verdict tells you everything the entry needs:
speaks_mcp: false→ the probe could not verify MCP. Stop and re-research — with one exception:reachable: trueplus the error "Initialize was rejected and no OAuth metadata was discovered" is the auth-walled API-key case (last bullet below).auth_flavor: "oauth_dcr"withpassed_activation_gate: true→ OAuth with Dynamic Client Registration. The entry isauth_type="oauth"and will activate automatically on merge.auth_flavor: "oauth_shared"→ OAuth without DCR. The entry isauth_type="oauth"but normally ships inactive; an operator must register an OAuth app with the vendor and paste credentials in Django admin (see the operator checklist below — include it in your PR description). If PostHog already provisions that exact OAuth app through an instance credential source, declare the reviewed source instead; catalog sync verifies and activates it without copying secrets.auth_flavor: "open"→ the handshake completed without credentials.auth_type="api_key"; activates automatically on merge.auth_flavor: "api_key_or_unknown"withreachable: true→ an auth-walled API-key server; a bare 401/403 gives the probe no MCP evidence.auth_type="api_key", but the entry ships inactive — verify it with a real install (Gate B) before adding it, and note in the PR that an operator flips it active in Django admin per environment (users bring their own key; nothing to provision).
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 Changed · +1 lines fec008187cb9
- 8d ago First seen · 82 lines · 107 tokens per session scan A 19d11184bc25
adding-mcp-store-servers is a skill published in the GitHub repository PostHog/posthog-foss (714 stars, last pushed today), licensed MIT. It adds 107 tokens to every session and 1,489 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 2026-08-30.
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