Get Tick Size

Polymarket-compat GET /tick-size/{token_id}.

Resolution order (freshest source wins):

1. CLOB WS overlay: if a recent tick_size_change event has been observed for this token, emit the post-change value. PM shrinks the tick from 0.01 → 0.001 when a book moves past 0.96 or below 0.04 (and grows back when the book pulls away). The two directions have asymmetric correctness consequences:

   • Grow (0.001 → 0.01): previously-valid 0.001-step quotes are no longer multiples of the new tick. PM rejects with INVALID_ORDER_MIN_TICK_SIZE. This is the case where missing the change silently breaks the bot.
   • Shrink (0.01 → 0.001): 0.01-step quotes are still valid multiples of 0.001, so orders aren’t rejected — but the bot is leaving precision on the table and quoting less competitively than the rest of the book. SDK porters reading PM docs expect tick refresh in both directions.

2. markets.minimum_tick_size column (populated by the Gamma sync from orderPriceMinTickSize).

3. 404 TOKEN_NOT_FOUND when the token doesn’t resolve to any market. A missing token returns 404 rather than a default 0.01 fallback — quoting on the wrong tick is a real-money risk for py-clob-client porters.

On transient upstream failure (DB/Redis unavailable) the handler returns 503 with Retry-After: 2, NOT a silent default tick.

Value consistency: the tick VALUE is resolved through :func:resolve_canonical_tick, the single source shared with GET /book and order validation, so all three surfaces agree. The tick-value chain remains network-free (allow_live_book=False): overlay → DB column → default, with NO per-read GET /book fetch. When the authoritative fallback flag is enabled, the preceding token-existence gate may consult the CLOB only after a local miss. /book reads keep seeding the overlay so this surface stays fresh without paying a book fetch on every read. This handler keeps the JSON-number wire shape (minimum_tick_size: 0.01) — PM emits /tick-size as a number, distinct from /book’s string tick_size; we change the value source, not the type. The token-existence (404) and upstream-failure (503) envelopes below are unchanged.