Graph Merge Suggestions

Instructions

Implementation Reference

• src/mcp-server/index.ts:698-749 (registration)

  Registration of the 'graph_merge_suggestions' MCP tool using the MCP SDK server.registerTool() with its description, input schema (Zod), and annotations.

  // ─── Tool: graph_merge_suggestions ───
  
  server.registerTool("graph_merge_suggestions", {
    title: "Graph Merge Suggestions",
    description:
      "Surface candidate pairs of entities likely to be duplicates. Read-only — never auto-merges. Combines embedding similarity, shared-neighbor overlap, and name-token Jaccard. Same-type only. Use to triage entity-explosion before running graph_merge (destructive consolidation) or graph_relate with ALIAS_OF (soft alias).",
    inputSchema: {
      entity_id: z.string().optional().describe("Scope to one entity's potential duplicates"),
      entity_type: z.string().optional().describe("Scope to one entity type (Person, Project, etc.)"),
      min_score: z.number().optional().describe("Combined-score threshold to surface (default 0.8)"),
      min_embedding_similarity: z.number().optional().describe("Embedding-similarity floor for candidates (default 0.85)"),
      limit: z.number().optional().describe("Max suggestions to return (default 20, max 100)"),
      weights: z.object({
        embedding: z.number().optional(),
        neighbor_jaccard: z.number().optional(),
        name: z.number().optional(),
      }).optional().describe("Override default weights (0.4 / 0.4 / 0.2)"),
      log_to_audit: z.boolean().optional().describe("Emit merge_flagged audit events for surfaced pairs (default true)"),
    },
    annotations: { readOnlyHint: true, destructiveHint: false, idempotentHint: true },
  }, async (args) => {
    try {
      const tenantId = currentTenant();
      const result = await client.mergeSuggestions(tenantId, {
        entity_id: args.entity_id,
        entity_type: args.entity_type as EntityType | undefined,
        min_score: args.min_score,
        min_embedding_similarity: args.min_embedding_similarity,
        limit: args.limit,
        weights: args.weights,
      });
  
      if (args.log_to_audit !== false) {
        for (const s of result.suggestions) {
          try {
            appendAuditEvent({
              event: "merge_flagged",
              timestamp: new Date().toISOString(),
              tenant_id: tenantId,
              entity_a: s.entity_a.id,
              entity_b: s.entity_b.id,
              reason: `score=${s.score} (emb=${s.signals.embedding_similarity}, neighbor_jaccard=${s.signals.neighbor_jaccard}, name=${s.signals.name_similarity})`,
            });
          } catch { /* audit is best-effort */ }
        }
      }
  
      return toolResult(result);
    } catch (err) {
      return toolError(`graph_merge_suggestions failed: ${err instanceof Error ? err.message : String(err)}`);
    }
  });

• src/mcp-server/index.ts:718-749 (handler)

  Tool handler for graph_merge_suggestions: calls client.mergeSuggestions() and optionally logs merge_flagged audit events for each suggestion.

  }, async (args) => {
    try {
      const tenantId = currentTenant();
      const result = await client.mergeSuggestions(tenantId, {
        entity_id: args.entity_id,
        entity_type: args.entity_type as EntityType | undefined,
        min_score: args.min_score,
        min_embedding_similarity: args.min_embedding_similarity,
        limit: args.limit,
        weights: args.weights,
      });
  
      if (args.log_to_audit !== false) {
        for (const s of result.suggestions) {
          try {
            appendAuditEvent({
              event: "merge_flagged",
              timestamp: new Date().toISOString(),
              tenant_id: tenantId,
              entity_a: s.entity_a.id,
              entity_b: s.entity_b.id,
              reason: `score=${s.score} (emb=${s.signals.embedding_similarity}, neighbor_jaccard=${s.signals.neighbor_jaccard}, name=${s.signals.name_similarity})`,
            });
          } catch { /* audit is best-effort */ }
        }
      }
  
      return toolResult(result);
    } catch (err) {
      return toolError(`graph_merge_suggestions failed: ${err instanceof Error ? err.message : String(err)}`);
    }
  });

• src/mcp-server/index.ts:704-716 (schema)

  Input schema (Zod) for graph_merge_suggestions: entity_id, entity_type, min_score, min_embedding_similarity, limit, weights (embedding/neighbor_jaccard/name), and log_to_audit.

  inputSchema: {
    entity_id: z.string().optional().describe("Scope to one entity's potential duplicates"),
    entity_type: z.string().optional().describe("Scope to one entity type (Person, Project, etc.)"),
    min_score: z.number().optional().describe("Combined-score threshold to surface (default 0.8)"),
    min_embedding_similarity: z.number().optional().describe("Embedding-similarity floor for candidates (default 0.85)"),
    limit: z.number().optional().describe("Max suggestions to return (default 20, max 100)"),
    weights: z.object({
      embedding: z.number().optional(),
      neighbor_jaccard: z.number().optional(),
      name: z.number().optional(),
    }).optional().describe("Override default weights (0.4 / 0.4 / 0.2)"),
    log_to_audit: z.boolean().optional().describe("Emit merge_flagged audit events for surfaced pairs (default true)"),
  },

• src/shared/neo4j-client.ts:1796-2047 (helper)

  Core mergeSuggestions() method on Neo4jClient that queries Neo4j for entity embeddings, finds similar same-type pairs via vector search, computes hub-aware neighbor Jaccard and name-token Jaccard, combines them into a weighted score, and returns suggestions sorted by score.

  async mergeSuggestions(
    tenantId: string,
    options: {
      entity_id?: string;
      entity_type?: EntityType;
      min_score?: number;
      min_embedding_similarity?: number;
      limit?: number;
      weights?: { embedding?: number; neighbor_jaccard?: number; name?: number };
    } = {},
  ): Promise<{
    suggestions: Array<{
      entity_a: { id: string; name: string; type: string; edge_count: number };
      entity_b: { id: string; name: string; type: string; edge_count: number };
      score: number;
      signals: {
        embedding_similarity: number;
        name_similarity: number;
        neighbor_jaccard: number;
        shared_neighbors: Array<{ id: string; relation: string; degree: number; weight: number }>;
      };
      recommended_action: "review";
    }>;
    total_pairs_evaluated: number;
    threshold_used: number;
    scope: { entity_id?: string; entity_type?: string; global: boolean };
  }> {
    const minScore = options.min_score ?? 0.8;
    const minEmbSim = options.min_embedding_similarity ?? 0.85;
    const limit = Math.min(options.limit ?? 20, 100);
    const w = {
      embedding: options.weights?.embedding ?? 0.4,
      neighbor_jaccard: options.weights?.neighbor_jaccard ?? 0.4,
      name: options.weights?.name ?? 0.2,
    };
    // Cap the number of seed entities to avoid runaway scans on large graphs.
    const MAX_SEEDS = 200;
  
    // Step 0: precompute per-entity edge degrees for hub-aware Jaccard.
    // A neighbor with degree D contributes weight 1/(1+log(D)) to the
    // intersection/union sums — so a 1-edge specific neighbor contributes
    // 1.0, while a 50-edge hub (e.g. the user's own Person node) contributes
    // ~0.20. Shared neighbors that are everyone's neighbor add little signal.
    const degreeRows = await this.run(
      `
      MATCH (n:Entity {tenant_id: $tenantId})
      RETURN n.id AS id, count{(n)-[]-(:Entity {tenant_id: $tenantId})} AS degree
      `,
      { tenantId },
    );
    const degrees = new Map<string, number>();
    for (const r of degreeRows) {
      degrees.set(String(r["id"]), Number(r["degree"] ?? 0));
    }
    const neighborWeight = (degree: number): number => {
      const d = Math.max(degree, 1);
      return 1 / (1 + Math.log(d));
    };
  
    // Step 1: collect seed entities. Constrained by entity_id / entity_type.
    const seedRows = await this.run(
      `
      MATCH (n:Entity {tenant_id: $tenantId})
      WHERE n.embedding IS NOT NULL
        AND ($entityId IS NULL OR n.id = $entityId)
        AND ($entityType IS NULL OR $entityType IN labels(n))
      RETURN n.id AS id,
             n.name AS name,
             n.embedding AS embedding,
             [l IN labels(n) WHERE l <> 'Entity'][0] AS type
      LIMIT $maxSeeds
      `,
      {
        tenantId,
        entityId: options.entity_id ?? null,
        entityType: options.entity_type ?? null,
        maxSeeds: MAX_SEEDS,
      },
    );
  
    // Step 2: for each seed, find vector-similar same-type neighbors and
    // build a deduped pair map. Pairs are canonicalised so a.id < b.id.
    type Pair = { idA: string; idB: string; embSim: number };
    const pairs = new Map<string, Pair>();
  
    for (const row of seedRows) {
      const seedId = String(row["id"]);
      const seedType = String(row["type"] ?? "");
      const seedEmbedding = row["embedding"] as number[] | null | undefined;
      if (!Array.isArray(seedEmbedding) || seedEmbedding.length === 0) continue;
      if (!seedType) continue;
  
      const similar = await this.vectorSearch(tenantId, seedEmbedding, {
        top_k: 10,
        min_similarity: minEmbSim,
        entity_types: [seedType as EntityType],
      });
  
      for (const candidate of similar) {
        if (candidate.id === seedId) continue; // self-match
        const [idA, idB] = seedId < candidate.id
          ? [seedId, candidate.id]
          : [candidate.id, seedId];
        const key = `${idA}::${idB}`;
        const existing = pairs.get(key);
        // Keep the higher embedding score if we see the same pair twice.
        if (!existing || candidate.score > existing.embSim) {
          pairs.set(key, { idA, idB, embSim: candidate.score });
        }
      }
    }
  
    const totalPairsEvaluated = pairs.size;
  
    // Step 3: per-pair feature query — names, types, edge counts, neighbors.
    const suggestions: Array<{
      entity_a: { id: string; name: string; type: string; edge_count: number };
      entity_b: { id: string; name: string; type: string; edge_count: number };
      score: number;
      signals: {
        embedding_similarity: number;
        name_similarity: number;
        neighbor_jaccard: number;
        shared_neighbors: Array<{ id: string; relation: string; degree: number; weight: number }>;
      };
      recommended_action: "review";
    }> = [];
  
    for (const pair of pairs.values()) {
      const featureRows = await this.run(
        `
        MATCH (a:Entity {tenant_id: $tenantId, id: $idA})
        MATCH (b:Entity {tenant_id: $tenantId, id: $idB})
        OPTIONAL MATCH (a)-[ra]-(na:Entity {tenant_id: $tenantId})
        WHERE na.id <> b.id
        WITH a, b, collect(DISTINCT na.id + '|' + type(ra)) AS neighborsA
        OPTIONAL MATCH (b)-[rb]-(nb:Entity {tenant_id: $tenantId})
        WHERE nb.id <> a.id
        WITH a, b, neighborsA,
             collect(DISTINCT nb.id + '|' + type(rb)) AS neighborsB
        RETURN a.name AS nameA,
               [l IN labels(a) WHERE l <> 'Entity'][0] AS typeA,
               b.name AS nameB,
               [l IN labels(b) WHERE l <> 'Entity'][0] AS typeB,
               neighborsA,
               neighborsB
        `,
        { tenantId, idA: pair.idA, idB: pair.idB },
      );
  
      if (featureRows.length === 0) continue;
      const f = featureRows[0]!;
      const neighborsA = (f["neighborsA"] as string[] | null | undefined ?? [])
        .filter((s) => typeof s === "string" && s.length > 0);
      const neighborsB = (f["neighborsB"] as string[] | null | undefined ?? [])
        .filter((s) => typeof s === "string" && s.length > 0);
  
      const setA = new Set(neighborsA);
      const setB = new Set(neighborsB);
      const intersection = neighborsA.filter((x) => setB.has(x));
      const unionSet = new Set([...neighborsA, ...neighborsB]);
      // Hub-aware weighted Jaccard. Each neighbor entry is "id|relation"; we
      // look up the global degree of the neighbor entity (id portion) and
      // weight its contribution inversely. A pair that shares only a hub
      // (everyone's neighbor) gets little credit; a pair that shares a
      // specific low-degree neighbor gets near-full credit.
      const idOf = (entry: string): string => {
        const sep = entry.lastIndexOf("|");
        return sep >= 0 ? entry.slice(0, sep) : entry;
      };
      let weightedInter = 0;
      for (const entry of intersection) {
        const deg = degrees.get(idOf(entry)) ?? 1;
        weightedInter += neighborWeight(deg);
      }
      let weightedUnion = 0;
      for (const entry of unionSet) {
        const deg = degrees.get(idOf(entry)) ?? 1;
        weightedUnion += neighborWeight(deg);
      }
      const neighborJaccard = weightedUnion === 0 ? 0 : weightedInter / weightedUnion;
  
      const nameA = String(f["nameA"] ?? "");
      const nameB = String(f["nameB"] ?? "");
      const tokensA = new Set(
        nameA.toLowerCase().split(/[^a-z0-9]+/).filter((t) => t.length > 0),
      );
      const tokensB = new Set(
        nameB.toLowerCase().split(/[^a-z0-9]+/).filter((t) => t.length > 0),
      );
      const tokenInter = [...tokensA].filter((t) => tokensB.has(t)).length;
      const tokenUnion = new Set([...tokensA, ...tokensB]).size;
      const nameSim = tokenUnion === 0 ? 0 : tokenInter / tokenUnion;
  
      const score =
        w.embedding * pair.embSim +
        w.neighbor_jaccard * neighborJaccard +
        w.name * nameSim;
  
      if (score < minScore) continue;
  
      const sharedNeighbors = intersection.map((entry) => {
        const sep = entry.lastIndexOf("|");
        const id = sep >= 0 ? entry.slice(0, sep) : entry;
        const relation = sep >= 0 ? entry.slice(sep + 1) : "";
        const deg = degrees.get(id) ?? 1;
        return {
          id,
          relation,
          degree: deg,
          weight: Number(neighborWeight(deg).toFixed(4)),
        };
      });
  
      suggestions.push({
        entity_a: {
          id: pair.idA,
          name: nameA,
          type: String(f["typeA"] ?? "?"),
          edge_count: setA.size,
        },
        entity_b: {
          id: pair.idB,
          name: nameB,
          type: String(f["typeB"] ?? "?"),
          edge_count: setB.size,
        },
        score: Number(score.toFixed(4)),
        signals: {
          embedding_similarity: Number(pair.embSim.toFixed(4)),
          name_similarity: Number(nameSim.toFixed(4)),
          neighbor_jaccard: Number(neighborJaccard.toFixed(4)),
          shared_neighbors: sharedNeighbors,
        },
        recommended_action: "review",
      });
    }
  
    suggestions.sort((a, b) => b.score - a.score);
    const truncated = suggestions.slice(0, limit);
  
    return {
      suggestions: truncated,
      total_pairs_evaluated: totalPairsEvaluated,
      threshold_used: minScore,
      scope: {
        entity_id: options.entity_id,
        entity_type: options.entity_type,
        global: !options.entity_id && !options.entity_type,
      },
    };
  }