The oversized source
One request, two costs: the GitHub compare endpoint answers with 1.26 MB — roughly 315k tokens. select trims it server-side to 28 KB, the fields alone, with the nested shape intact. Re-verified 8 Aug 2026, provenance included.
The research question
"Summarise what changed between these two releases." The GitHub compare endpoint has the answer — wrapped in 52 commits with author objects, trees and verification blocks, then 183 per-file patches. The source itself is the problem. Captured payloads, re-verified 8 Aug 2026.
One request, two costs
Fetched whole, the response overflows the agent's context. The jq-lite path commits[].commit.message reaches into every array element server-side and preserves the nested shape, so rows stay aligned. Same request, side by side:
// the same request, no select fetch("https://api.github.com/repos/ggml-org/llama.cpp/compare/b10256...b10308") // returns — truncated { "url": "https://api.github.com/repos/…", "html_url": "…", "permalink_url": "…", "diff_url": "…", "patch_url": "…", "base_commit": { "sha": "…", "node_id": "…", "commit": { "author": {…}, "committer": {…}, "tree": {…}, "verification": {…} }, … }, "merge_base_commit": {…}, "status": "ahead", "ahead_by": 52, "commits": [ { "sha": "22dc605c4ead…", "node_id": "…", "commit": {…}, "author": {…}, "committer": {…}, "parents": […] }, … 51 more ], "files": [ { "sha": "289e5144e63c…", "filename": ".github/workflows/build-apple.yml", "blob_url": "…", "patch": "@@ -541,7 +541,9 @@ …" }, … 182 more ] }
// the same request, with select fetch("https://api.github.com/repos/ggml-org/llama.cpp/compare/b10256...b10308", select: ["ahead_by", "total_commits", "commits[].sha", "commits[].commit.message"]) // returns { "ahead_by": 52, "total_commits": 52, "commits": [ { "sha": "22dc605c4ead…", "commit": { "message": "ci: fix vulkan llvmpipe runs (#26533)" } }, { "sha": "935cad6497e8…", "commit": { "message": "llama : move n_vocab from llama_sampler…" } }, … 50 more ] }
Measured improvement, and where this came from
28 KB (~7k tokens) reached the agent instead of 1.26 MB (~315k) — the answer to the question, with every commit message intact. The source stays cached for 24 hours, so follow-ups are free. The finished summary built from exactly this payload is the nightly release digest.
client Claude Code over MCP re-verified 8 Aug 2026 — schema: true → commits[] $items: 52 · files[] $items: 183; select rerun → identical ahead_by: 52 payload source full 1.26 MB response linked above — check the trim yourself retention body cached server-side · 24 h