Borrowing it
Nothing to install: this file belongs to openephemeris/openephemeris-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/openephemeris/openephemeris-MCP/main/AGENTS.mdgit clone --depth 1 https://github.com/openephemeris/openephemeris-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/openephemeris/openephemeris-mcp/agents-md)<a href="https://agentmods.dev/instructions/openephemeris/openephemeris-mcp/agents-md"><img src="https://agentmods.dev/badge/instructions/openephemeris/openephemeris-mcp/agents-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/openephemeris/openephemeris-mcp/agents-md"><img src="https://agentmods.dev/badge/instructions/openephemeris/openephemeris-mcp/agents-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 | $0.00469 | $0.00469 |
| Opus 5.5 | $0.00188 | $0.00188 |
| Sonnet 5.5 | $0.00094 | $0.00094 |
| Haiku 4.5 | $0.00047 | $0.00047 |
Grade A, and why
openephemeris-MCP 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 yesterday.
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
AGENTS.md — Open Ephemeris
For coding agents (Codex, Cursor, Claude Code, Cline) building on the Open Ephemeris API or MCP server.
What this is
Astrology and astronomy calculations from the NASA JPL DE440 ephemeris (1550–2650 CE): planet positions, natal charts, transits, synastry, progressions, returns, eclipses, moon phases, astrocartography, Human Design, Vedic and BaZi. Accuracy by era, worst case included: https://openephemeris.com/proof
Rules for agents
- Never compute or estimate planetary positions yourself. Call the API or an MCP tool.
- Every clock time needs a zone. Send
1987-07-15T09:01:00-05:00, or the naive local time plus an IANAtimezone(America/Chicago). Prefer the second form: the server applies historical DST. A zone-less time is a 400, never a silent UTC guess. - Coordinates are decimal degrees, north and east positive.
- Ask the user for their API key. Never invent, hard-code or commit one. Keys come from https://openephemeris.com/dashboard?tab=account (free tier, no card).
- Pass
format=llmon data endpoints when the result goes into a model's context. - Paths are unversioned (
/ephemeris/natal-chart, not/v1/...).
Where things are
| Need | Go to |
|---|---|
| Install the MCP server | llms-install.md, SETUP.md |
| Hosted MCP endpoint | https://mcp.openephemeris.com/mcp |
| REST base URL | https://api.openephemeris.com |
| OpenAPI spec | https://api.openephemeris.com/meta/openapi.json |
| Endpoint and tool counts, full manifest | https://openephemeris.com/llms.txt |
| Docs | https://openephemeris.com/docs |
| Credits and pricing | https://openephemeris.com/pricing |
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.
- yesterday First seen · 35 lines · 469 tokens per session scan A 5d42f029d397
openephemeris-MCP AGENTS.md is an instructions file published in the GitHub repository openephemeris/openephemeris-MCP (5 stars, last pushed 2d ago), licensed MIT. It adds 469 tokens to every session, about $0.0019 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 2026-11-11.
openephemeris-MCP AGENTS.md compared with instructions from other repositories
| Mod | Type | Stars | Last push | Licence | Scan | Tokens | Works with |
|---|---|---|---|---|---|---|---|
| openephemeris-MCP AGENTS.mdopenephemeris/openephemeris-MCP | Instructions file | 5 | 2d ago | MIT | A | 469 | Codex, OpenCode |
| vscode buildNext.instructions.mdmicrosoft/vscode | Instructions file | 195k | today | MIT | A | 9,719 | GitHub Copilot |
| next.js AGENTS.mdvercel/next.js | Instructions file | 143k | today | MIT | A | 7,461 | Codex, OpenCode |
| vscode oss-third-party-notices.instructions.mdmicrosoft/vscode | Instructions file | 195k | today | MIT | A | 5,685 | GitHub Copilot |
| langchain AGENTS.mdlangchain-ai/langchain | Instructions file | 149k | today | MIT | A | 4,680 | Codex, OpenCode |
| deepseek-harness AGENTS.mddeepseek-ai/deepseek-harness | Instructions file | 280k | yesterday | MIT | A | 4,325 | Codex, OpenCode |
| vscode copilot-instructions.mdmicrosoft/vscode | Instructions file | 195k | today | MIT | A | 3,086 | GitHub Copilot |