Why OpenAI Codex / Codex CLI Needs Explicit Neon Schema Context
OpenAI Codex / Codex CLI is OpenAI's coding agent and Codex CLI. Like all LLM-powered coding tools, it has no native awareness of your database. Without explicit schema context, it will hallucinate JOIN paths, reference non-existent columns, query sensitive fields, and waste thousands of tokens per prompt.
Schemap solves this by extracting your live Neon schema and compiling it into AGENTS.md — a file OpenAI Codex / Codex CLI reads automatically from your project root.
Quickstart: Neon + OpenAI Codex / Codex CLI in 3 Steps
Step 1 — Install Schemap
pipx install schemap-tool
# or: uv tool install schemap-toolStep 2 — Connect to Neon
schemap quickstart
# Enter: postgresql://[user]:[password]@[endpoint].neon.tech/[dbname]?sslmode=requireStep 3 — Generate AGENTS.md database context
schemap agents --targets codex
# Wrote AGENTS.md with safety guardrails in 2msWhat Schemap Injects into AGENTS.md
- Table Map — every Neon Postgres table with column types
- Foreign Key Graph — explicit JOIN relationships, no guessing
- Centrality Scores — most-connected tables highlighted
- [SAFETY] Guardrails — blocks sensitive column access and audit table mutation
- Candidate FK Detection — inferred missing relationships from naming patterns
Token Cost Savings on Neon Schemas
Raw Neon Postgres DDL dumps run 15,000–80,000 tokens. Schemap reduces that by 89%%. Run schemap benchmark --cost to calculate your exact monthly savings.
Keep Context in Sync Automatically
schemap hook install
# Auto-regenerates AGENTS.md on every migration commitFrequently Asked Questions
How do I give OpenAI Codex / Codex CLI Neon database context?
Install Schemap with pipx install schemap-tool, connect to your Neon Postgres database (postgresql://[user]:[password]@[endpoint].neon.tech/[dbname]?sslmode=require), then run schemap agents --targets codex to auto-generate AGENTS.md with full schema context, foreign key maps, and anti-hallucination safety rules.
Does Schemap support Neon with OpenAI Codex / Codex CLI?
Yes. Schemap fully supports Neon (the serverless multi-tenant PostgreSQL cloud architecture) and generates native AGENTS.md database context that OpenAI Codex / Codex CLI reads automatically from your project directory.
What makes Schemap better than manually writing AGENTS.md for Neon Postgres?
Manual schema files go stale instantly. Schemap runs in sub-3ms, auto-infers foreign keys, injects SAFETY guardrails, and compresses your Neon Postgres schema by up to 89%% so OpenAI Codex / Codex CLI always has accurate context.
Ready to give OpenAI Codex / Codex CLI accurate Neon context?
Free for up to 100 tables. No cloud sync. Schema stays local.
Install Schemap Free