emem — Earth memory protocol

Resolves a place mention (free-text name, address, or lat/lng) to the protocol's cell64 identifier, and returns the topic-grouped inventory of bands and algorithms available at that location. When to use: Use whenever the input refers to a real-world location and the next step needs the cell64 identifier or wants to know which bands are available before recalling. The response carries `data_at_this_cell` with three sub-fields: `live_bands_by_topic` (every band recallable here, grouped by topic such as flood_water_event_window, vegetation_condition, built_up_human_geography), `algorithms_for_topic` (composition recipes that fuse those bands into named scores), and `declared_but_no_materializer_at_this_responder` (cube slots reserved without a live connector). For the single-shot path that runs the full chain server-side and returns one packaged answer, use `emem_ask` instead.

Single-shot free-text answer about a real-world location, backed by signed satellite/elevation/water/built-up receipts. Forwards a place mention plus a question; runs the locate → recall → algorithm chain server-side; returns one packaged envelope. When to use: Use when the question concerns a specific real-world place and a packaged, citation-bearing answer is preferable to manual primitive composition. Forward the user's question verbatim as `q` plus the location as `place` (free text), `cell` (cell64), or `lat`+`lng`. The server resolves the location, classifies the question to a topic, recalls every relevant band (auto-materializing Sentinel-2 / Sentinel-1 / Cop-DEM / JRC GSW / Overture / weather on miss), surfaces the algorithm recipes that compose those bands into named scores, and returns a single envelope with `topic_routing`, `facts`, `algorithms_for_question`, an optional Sentinel-2 RGB scene URL, and a `caveats` block (grid resolution, revisit cadence). All facts are signed by the responder; the receipt's `fact_cids` are content-addressed and citable. Set `include_image: true` to bundle the latest cloud-free Sentinel-2 thumbnail. Out-of-scope questions return `topic_routing.matched_topic: null` plus the full inventory so the caller can route elsewhere.

Recall facts about a cell — auto-materializes on miss for any band with a registered materializer. When to use: Call after `emem_locate` (or with a known cell64). Returns every Primary fact stored at that (cell, band, tslot). IMPORTANT: if the cell has no fact yet for a requested band AND that band has `has_materializer=true` (per `emem_coverage_matrix` / `emem_materializers`), the responder fetches the upstream value, signs it under its identity, persists it, and returns it in the same response (~180 ms first call, ~10 ms cached thereafter). So for any wired band you can recall ANY cell on Earth without seeding — just pass `bands: [<band>]`. The response carries `materialize_notes` listing what was just fetched. Empty result with no notes means the band has no materializer at this responder.

Recall facts across every cell inside a place's polygon (single signed envelope). Closes the place-name-drift gap for wide features (parks, lakes, regions). When to use: Call when the user names a wide feature (national park, river basin, country, large urban area) where one cell is too small. Pass `place` and the geocoder will fan out across the polygon — or pass `polygon_bbox` directly if you have coordinates. Returns `merged_facts`, `by_cell`, and a `polygon_bbox.source` indicator (`nominatim_boundingbox` = real polygon, `centre_cell_bbox` = fallback to one cell because the geocoder had no polygon).

Query facts over a region (single cell or list of cells), optionally aggregated per band. When to use: Call when the user asks 'how does region X look', 'what's the average NDVI here', or wants a region-level summary. Use `agg=mean|median|p90|vector_centroid` to fold per-band values.

Compare two cells: cosine similarity over shared vector bands + per-band scalar deltas. When to use: Call when the user asks 'how similar is X to Y', 'compare these two places', or wants a difference vector. Returns a single cosine score and per-band deltas.

Compare two bands at the same cell. Scalar pair → metric=delta, value=b-a. Vector pair (equal dim) → metric=cosine + per-dim delta. Returns a signed receipt naming both source fact CIDs. When to use: Call when the user wants cross-source consistency at one place ('does Cop-DEM agree with GMRT here?'), cross-vintage drift ('how did the embedding change between 2017 and 2024 at this cell?'), or any band-vs-band comparison within a single cell. `cell` + `a` + `b` are required; `tslot_a`/`tslot_b` default to 0 (the static slot used by Cop-DEM, GMRT, ESA WorldCover, etc.).

k-NN over the corpus by cell embedding or inline vector. When to use: Call when the user asks 'find places like X', 'where else looks like this', or hands an embedding to find neighbours. `key` is either a cell64 or `inline:[x,y,...]`. Default band is `geotessera` (128-D Tessera foundation embedding); pass `band: "geotessera.multi_year"` for the 1024-D 8-vintage fusion.

Time series for one (cell, band) over an inclusive [start, end] tslot window. Returns only what's already attested — does NOT trigger materialization. For historical backfill use `emem_backfill`. When to use: Call when the user asks 'how did X change over time' for a band that already has multiple historical tslots seeded. IMPORTANT differences from `emem_recall`: (1) trajectory does NOT auto-materialize past tslots — it returns only facts that have already been attested at this responder, so for fast-tempo bands like `indices.ndwi` you'll typically see ONE point at the latest tslot until an attester seeds history. (2) tslots are non-negative `u64`; there's no negative-offset 'last 2 years' shorthand. For LONG-TERM history questions ('flooded in last 2 years', 'forest loss since 2020') prefer either (a) a static-tempo summary band that one fact answers — `surface_water.recurrence` covers 1984-2021 in a single signed value, no trajectory needed — or (b) `emem_backfill` to materialize and sign the missing tslots in one call.

Compute a DerivativeFact (delta) between a band's values at two tslots. When to use: Call when the user asks 'what changed between t1 and t2', 'give me the delta'. Returns a signed DerivativeFact + receipt — the delta itself is content-addressed and citable.

Fetch a fact by its content-address (CID). Returns the full signed Primary or Absence fact — the same body served by REST `/v1/facts/{cid}`. Closes the citation loop: any fact_cid surfaced by recall, materialize, attest, or verify can be re-resolved by another agent without REST. When to use: Call whenever you have a `fact_cid` (e.g. from `emem_recall`'s response, an `emem_attest` receipt, an `emem_materializers` outcome, or a citation in another agent's reply) and need the full fact body — its value, unit, sources, signer, signed_at, and derivation. Particularly useful for verifying that a citation a downstream agent gave you actually resolves on this responder. The response is byte-identical across responders for the same CID — the CID itself is the validator.

Materialize and sign every per-tslot fact for one (cell, band) inside a [start_unix, end_unix] window. Returns a signed list of (tslot, fact_cid, status) for each step. Slow but possible — one upstream fetch per tslot, capped by `max_facts`. When to use: Call when the user wants HISTORY for a fast/medium-tempo band and `emem_trajectory` returned only the latest point. The responder iterates the tslot range derived from the band's tempo, calls the per-tslot historical materializer, signs each result, and persists. After completion `emem_trajectory` over the same window returns the full series. Bands without a historical materializer (e.g. `weather.*` from met.no's nowcast) return `status: "present_only"` for past tslots — check `emem_coverage_matrix.history_available_from`/`history_available_to` to see how far back each band can be backfilled. Prefer this over staking an attestation when the upstream is publicly fetchable.

Verify a structured claim against a cell's facts. Returns verdict + evidence CIDs + signed receipt. When to use: Call when the user asks a yes/no question about a cell ('is the NDVI > 0.7 here', 'has this been deforested'), or when downstream code wants citable evidence for a logical predicate.

True-colour Sentinel-2 L2A RGB thumbnail centred on a cell. PNG returned as a native MCP ImageContent block (mimeType image/png). Pure-Rust pipeline: STAC search + HTTP-Range COG reads + 2-98 percentile stretch + PNG encode. When to use: Call when the user wants a VISUAL of a place — 'show me what this looks like', 'before/after the flood', 'is there a forest here', 'is this developed'. Returns a 256×256 px RGB image (~2.56 km × ~2.56 km at S2's 10 m native resolution), centred on the cell. Pass `cell` as a cell64 string OR a place name (auto-resolved). `max_cloud` filters scenes by `eo:cloud_cover` (default 20 %); raise it (60–80 %) for cloud-prone tropics if you keep getting 'no scene' errors. `datetime` is an RFC 3339 interval like `"2024-01-01T00:00:00Z/2024-12-31T00:00:00Z"` for a temporal slice (defaults to last 90 days). `structuredContent` carries the STAC item id, capture time, cloud_cover, EPSG, and per-channel reflectance percentile stretch values used — quote those alongside the image so the receipt is reproducible.

Cell polygon as a native MCP EmbeddedResource (mimeType application/geo+json). Properties carry centre lat/lng, bbox, approx size in metres, and the 8-cell neighbourhood — drop straight into Mapbox / Leaflet / Deck.gl / QGIS without a GIS pipeline. When to use: Call when the agent (or a downstream renderer) needs the cell as geographic geometry — for map overlays, polygon-clipping ops, or feeding a styling pipeline. Pass `cell` as cell64 or place name. The result is a GeoJSON Feature with Polygon geometry; for a FeatureCollection that includes every recalled fact's value as a property, fetch /v1/cells/{cell64}/recall_geojson?bands=... over plain REST instead.

Submit a typed Intent; receive a plan or executed result. When to use: Call when the user asks something like 'where is X' or 'is A like B' and you don't want to pick a primitive yourself — the planner maps Intent variants to the right tool call.