Attribution Tags

Tags are the core attribution mechanism in Kostrack — every API call carries a dict of key-value pairs you define.

Setting tags on the client

Tags set on the client apply to every call made with that client:

client = Anthropic(tags={
    "project":     "openmanagr",
    "feature":     "invoice-extraction",
    "team":        "engineering",
    "environment": "production",
    "user_id":     "user_123",
})

Per-call overrides

Override or add tags for a specific call using kostrack_tags:

client.messages.create(
    model="claude-sonnet-4-6",
    max_tokens=512,
    messages=[...],
    kostrack_tags={
        "feature": "different-feature",
        "ab_test": "variant-b",
    }
)

Reserved keys

These keys appear as dropdown variables in the Grafana Overview dashboard:

Custom keys

Any key beyond the reserved set is stored in the JSONB tags column and GIN-indexed for fast queries:

-- Spend by A/B test variant
SELECT tags->>'ab_test' AS variant, SUM(cost_usd)
FROM llm_calls
WHERE tags ? 'ab_test'
GROUP BY 1;