Add Limits and Maximum Payload Size

[caleb-mabry]

Purpose

Add a limit to all calls. Also add a max payload size so the server does not flood our API with too much data.

Test this yourself?
Provide a DATABASE_URI environment variable such as postgresql://myusername:mypassword@127.0.0.1:5432/mydb

uv sync
uv run postgres-mcp --transport streamable-http
(Connect with http://localhost:8000/mcp)

uv run postgres-mcp --transport sse
(Connect with http://localhost:8000/sse)

What happens if...

I don't specify pageSize?

Returns first 100 rows (default_page_size)

I request more than 500 rows?

API validation rejects the request (max_page_size limit)

My query already has LIMIT 1000?

Your LIMIT is respected, pagination is not applied
However, if result exceeds 1MB payload size, you'll get an error

My 100 rows exceed 1MB?

Query executes but returns error: "Query result payload too large: X.XXMb exceeds maximum allowed size of 1MB"
Error suggests using LIMIT/OFFSET, filtering, or refining the query

I need to paginate through results?

First page: pageSize=100, offset=0
Second page: pageSize=100, offset=100
Third page: pageSize=100, offset=200, etc.