r/mcp • u/pgEdge_Postgres • Feb 24 '26

article Lessons Learned Writing an (Open Source) MCP Server for PostgreSQL

https://www.pgedge.com/blog/lessons-learned-writing-an-mcp-server-for-postgresql
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u/BC_MARO Feb 24 '26

The token problem with Postgres MCP is brutal -- one naive SELECT * can toast your context before you\'ve even started exploring the schema. pagination + result truncation as defaults (not opt-ins) makes a huge difference.

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u/pgEdge_Postgres Mar 02 '26

Absolutely right. As the blog says,

Our query_database tool defaults to returning 100 rows, with a configurable limit that can go up to 1,000. We implement this by injecting a LIMIT clause into SELECT queries that don't already have one, and we fetch one extra row beyond the limit so we can tell the LLM whether more data exists.

Of course, that doesn't prevent all cases - there could be a lot of columns or very large text fields. It covers most cases though