An 83-Tool MCP Server Cut AI Bad Calls to 1 in 290: Four Lessons
fcf41 · reddit · 2026-10-30
The developer of Editmamei, an MCP server for desktop Photoshop, shares how he reduced failed tool calls in a server with 83 tools. Glama's rubric flags 25+ tools as "too many," but a photo editor has hundreds of operations, so instead of cutting tools he tracked how often the model actually sends a bad call.
Since June: 61,977 tool calls, 98.2% ran without error; overall failures fell from 3.5% in August to 1.7% in October. Failures split two ways: bad calls from the AI (schema mismatch, unknown option, missing layer) were just 0.35% of calls in October, about 1 in 290; the other 80% of failures were Photoshop timeouts, file access and Photoshop not running. Users run it from Claude Desktop, Claude Code, Cursor and others.
Four things he credits:
- Distinct tools: descriptions say when to use each and which neighbor to pick instead
- One tool per job: parameters cover variations, e.g. psfilter covers 18 filter types and 5 operations with per-type argument checks
- Errors that list what's allowed: a bad call gets fixed on the next try
- A map: a short overview plus a 16-group capability map lets the model orient before choosing
He also notes Cloudflare's alternative: two tools (search and execute) covering 2,500+ API endpoints, with the model writing code against a typed API, and asks whether anyone has migrated a large server to that pattern.
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