STAC MCP Server

# ASR 1007: Offline Mock STAC Server for Testing Status: Proposed Date: 2025-09-23 ## Context To expand feature coverage (pagination, CQL2 filters, capabilities endpoints, aggregations) we need richer test scenarios than simple method patching while still preserving offline, fast execution (ASR 1001). A minimal in‑process mock STAC service (data served from static JSON fixtures) enables deterministic tests for new tools (ADR 0003, ADR 0004) without real network calls. ## Requirement * Provide a mock STAC API layer exposing endpoints: `/`, `/collections`, `/collections/{id}`, `/search`, `/conformance`, `/collections/{id}/queryables`, and optional `/aggregations` (namespaced if needed) returning static or parameter‑aware JSON. * Must run fully in‑process (no actual sockets) using a lightweight ASGI app or simple function dispatcher; tests call it through a custom `StacApiIO` adapter or by monkeypatching `Client.open`. * Response variants needed for tests: - Pagination (next links, matched counts) - Aggregations (histogram shell) - Error cases (4xx/5xx) to validate error mapping layer * Include fixtures under `tests/fixtures/mock_stac/` with minimal, valid STAC JSON fragments. * Execution time per test set < 50 ms (aggregate overhead minimal). * Deterministic: no reliance on clock except for fixed timestamps in fixtures. ## Implications * Simplifies implementing and validating future ADRs before acceptance. * Slight maintenance cost to update fixture shape when STAC spec evolves; keep scope narrow (only necessary fields). * Encourages earlier detection of pagination / filter regressions. ## Alternatives considered * Live network calls to public STAC APIs — rejected (non‑deterministic, potential rate limits). * Large recorded cassettes (e.g., via VCR) — heavier to curate and version; simpler handcrafted fixtures suffice for current scope. ## Addendums * Future: Add dynamic query evaluation (CQL2 parsing) if/when ADR 0003 is accepted and implemented.