edmundmiller Context Efficiency: Filter at the Source
Every token of noise in context is a token the model spends navigating instead of reasoning. Spend a few tokens on a precise query; save many on the backend.
Decision tree
Does the tool support structured output? (--json, -o json, --format json)
├─ Yes → select fields with jg when available; if `command -v jg` fails, use tool-native selectors, python3 -c, or jq instead of retrying
└─ No → pre-filter with path scopes, grep, head, API params, or SQL LIMIT
Structured-output patterns
# Select one field or path
tool -o json | jg 'precise.selector'
# Select a set of fields from each array item via disjunction
tool -o json | jg '[*].(id|name|status)'
# Transform when selection is not enough
tool -o json | python3 -c 'import json,sys; print(json.load(sys.stdin)[0]["field"])'
jq/python fallback patterns
Use these when the transformation is value-based filtering (not just path
selection) that jg's path-query language cannot express.
# python3 -c patterns
# Count by state
tool -o json | python3 -c "
import json, sys; d = json.load(sys.stdin)
from collections import Counter; print(Counter(x['state'] for x in d))
"
# Find matching entity
tool -o json | python3 -c "
import json, sys; d = json.load(sys.stdin)
print(next(x['entity_id'] for x in d if 'couch' in x['attributes'].get('friendly_name','').lower()))
"
Bounded command output
Before running commands that can dump a tree, log, search result, build output,
or API collection, add a path scope, --limit, head, structured selector, or
SQL LIMIT. Do not raise output-token caps to compensate for an unbounded
command. If output truncates, rerun a narrower command instead of scanning the
dump.
Oversized tool results
If a read, MCP call, or CLI returns "output too large" or saves overflow to a file, do not retry the same broad request. Recover with a narrower query:
- Re-run the source tool with tighter fields, date ranges, IDs, channel/project filters, or lower limits.
- If the tool saved an overflow artifact, search or read only the relevant ranges from that saved file.
- Prefer summaries or metadata endpoints before transcripts, full logs, Slack exports, calendar event lists, or issue dumps.
# ❌ broad transcript/log dump
tool get-transcript --id "$id"
# ✅ metadata or filtered content first
tool get-notes --id "$id"
tool search --query '"exact error" after:2026-01-01' --limit 5
Tool-specific examples
Home Assistant (hass-cli)
hass-cli -o json state list 'light.*' | jg '[*].(entity_id|state|attributes.friendly_name)'
hass-cli -o json area list | jg '[*].(area_id|name)'
hass-cli -o json device list | jq '[.[] | select(.area_id=="kitchen") | {id,name,area_id}]'
GitHub CLI
gh pr checks 42 --json name,state | jq '[.[] | select(.state!="SUCCESS") | .name]'
gh issue list --json number,title,labels --limit 30 | jq '[.[] | select(.labels[].name=="bug") | {number,title}]'
gh api repos/:owner/:repo/pulls --jq '.[].head.ref'
Nix
nix eval .#packages.aarch64-darwin --apply builtins.attrNames --json | jg '[*]'
Database
-- Always: WHERE + LIMIT over SELECT *
SELECT entity_id, state FROM states WHERE domain = 'light' ORDER BY last_changed DESC LIMIT 20;
Anti-patterns
# ❌ dumps hundreds of entities to find one
hass-cli state list
# ✅ returns exactly what you need
hass-cli -o json state list 'light.*' | jq '.[] | select(.attributes.friendly_name | test("desk"; "i"))'
# ❌ loads full PR list into context
gh pr list
# ✅ targeted
gh pr list --json number,title --limit 30 | jq '[.[] | select(.title | test("fix";"i"))]'