Analysis of 50 MCP servers: a third of tool lists are duplicated schema text
atp_studio_coll · reddit · 2026-11-13
The author pulled tools/list from 50 public MCP servers with long tool lists and found the problem isn't bloated descriptions — it's the same JSON pasted repeatedly:
- 23 of 50 servers had at least a third of the list as verbatim-repeated schema text (counting only blocks of a few hundred characters+)
- The usual culprit is a response envelope (status, warnings, sources, timing, nextactions) attached to every tool. One server declares the same long block on 74 of 75 tools; a calculator server ships an identical outputSchema on every tool. Inputs repeat too: a pressure-unit enum on 30 parameters, a leap-year date regex on every timestamp field
Cause: schemas are generated from shared types in code, but the wire protocol can't say "same as before" — $defs work within one tool, but two tools can't share a definition.
Cheap fixes: omit the optional outputSchema and describe the envelope once in server instructions; validate long patterns server-side and explain in a one-line field description.
Caveats: a third of servers barely repeat and are heavy for other reasons; untested whether models use tools worse without outputSchema.
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