accessing-osprey

name	accessing-osprey
description	Understanding the Osprey moderation infrastructure — system architecture, ClickHouse data access, schema reference, and relationship to Ozone labelling. Use when investigating AT Protocol accounts or reviewing rule execution data.
user-invocable	false

Accessing Osprey

This skill provides foundational knowledge for accessing, understanding, and querying Osprey rule execution data in ClickHouse. Use this when you need to investigate rule matches, account behavior, or rule performance.

What Is Osprey

Osprey is a moderation rule engine for the AT Protocol (Bluesky). It runs continuously, evaluates user-defined rules against the global firehose of posts and other events, and records the results in a ClickHouse table called osprey_execution_results.

Rules in Osprey are written in SML (a Python-like domain-specific language). Each rule is a predicate that returns true/false or a numeric score indicating whether a piece of content or an account matches the rule criteria.

Key point: Osprey detects. It does not label or enforce policy directly. Its output informs human moderators and automated systems (like Ozone) about which accounts or posts match which rules.

System Topology

AT Protocol Firehose
    ↓
Osprey Rule Engine (runs continuously)
    ├─ Reads: All posts, profiles, follows, other events
    ├─ Applies: User-defined rules (SML)
    ├─ Records: Execution results in ClickHouse
    └─ Outputs: osprey_execution_results table
        ↓
    ┌───────────────────────────────────┐
    │ Statistical Sidecars              │
    │ (read osprey_execution_results,   │
    │  write to their own tables)       │
    ├─ account_entropy → account_entropy_results
    ├─ url_overdispersion → url_overdispersion_results
    ├─ url_cosharing → url_cosharing_pairs, _clusters, _membership
    ├─ quote_overdispersion → quote_overdispersion_results
    ├─ quote_cosharing → quote_cosharing_pairs, _clusters, _membership
    └─ signup_anomaly → pds_signup_anomalies
        ↓
Investigation / Analysis / Labelling Decisions

Statistical Sidecars

Six sidecar services run alongside Osprey, reading from osprey_execution_results and producing scored output in their own ClickHouse tables. They flag — they don't label or take action. Their output feeds into investigations as starting points.

Account Entropy Sidecar

Table: account_entropy_results Purpose: Detect automated/bot-like posting patterns using temporal distribution analysis.

Computes Shannon entropy over two dimensions:

• Hourly entropy — how uniformly an account posts across 24 hours. High entropy (≥ 3.9) = posts around the clock = bot signature.
• Inter-post interval entropy — how regular the gaps between posts are. Low entropy (≤ 1.5) = mechanical spacing = bot signature.

The is_bot_like flag fires only when BOTH signals independently cross their thresholds (conjunction logic). This substantially reduces false positives — a shift worker or insomniac trips hourly entropy alone, a live-tweeter trips interval entropy alone, but only automation trips both.

Key columns: user_id (DID), hourly_entropy, interval_entropy, is_bot_like, hourly_flag, interval_flag, mean_interval_seconds, stddev_interval_seconds, sample_rkeys.

Runs every hour, analyses 7-day windows, requires ≥ 10 posts.

URL Overdispersion Sidecar

Table: url_overdispersion_results Purpose: Detect coordinated domain sharing campaigns using statistical anomaly detection.

Computes two independent signals per domain per time bucket:

• Volume anomaly (Poisson model) — is the observed share count statistically unlikely given the domain's baseline rate?
• Sharer density anomaly (normal approximation) — is the ratio of unique sharers to total shares unusually high? (Many accounts each sharing once = coordination.)

Either signal alone can flag a domain as anomalous (is_anomaly = 1). Uses entity baselines (domain's own history over 14 days) when available, falling back to population median for new/rare domains. Produces results at both hourly and daily granularity.

Key columns: domain, granularity, total_shares, unique_sharers, sharer_density, volume_p_value, density_p_value, is_anomaly, baseline_source, sample_dids, sample_urls, on_watchlist.

Runs every 15 minutes, requires ≥ 3 unique sharers.

URL Co-Sharing Sidecar

Tables: url_cosharing_pairs, url_cosharing_clusters, url_cosharing_membership Purpose: Detect coordinated inauthentic behaviour by finding clusters of accounts that repeatedly share the same URLs on the same day.

Builds a weighted graph (nodes = accounts, edge weight = number of co-shared URLs), runs Leiden community detection, and tracks how clusters evolve day-to-day. Three outputs:

• Pairs (url_cosharing_pairs) — daily account pairs with co-shared URLs. TTL 7 days.
• Clusters (url_cosharing_clusters) — cluster-level metrics, evolution classification, sample members/URLs. No TTL.
• Membership (url_cosharing_membership) — daily membership snapshots. TTL 7 days.

Key columns: cluster_id (stable ID), member_count, evolution_type (birth/death/continuation/merge/split), temporal_spread_hours, mean_posting_interval_seconds, sample_dids, sample_urls.

Runs daily. Minimum 3 accounts per cluster, minimum 2 co-shares per edge, minimum 3 accounts sharing a URL before it qualifies.

Dedicated MCP tools: Use cosharing_clusters, cosharing_pairs, cosharing_evolution for structured access (these support JOINs across the three tables internally). Use clickhouse_query for ad-hoc queries.

Quote Co-Sharing Sidecar

Tables: quote_cosharing_pairs, quote_cosharing_clusters, quote_cosharing_membership Purpose: Detect coordinated quote-post amplification by finding clusters of accounts that repeatedly quote the same posts on the same day.

Same architecture as URL co-sharing but tracks quote-posts instead of URL shares. Builds a weighted graph where edge weight = number of co-quoted AT-URIs, runs Leiden community detection, and tracks cluster evolution.

• Pairs (quote_cosharing_pairs) — daily account pairs with co-quoted posts. Uses shared_uris (AT-URIs). TTL 7 days.
• Clusters (quote_cosharing_clusters) — cluster-level metrics. Uses unique_uris and sample_uris (AT-URIs). No TTL.
• Membership (quote_cosharing_membership) — daily membership snapshots. TTL 7 days.

Detects pile-ons, brigading, and astroturfing via coordinated quoting. Cross-reference with url_cosharing_* to find accounts coordinating across both sharing and quoting.

Quote Overdispersion Sidecar

Table: quote_overdispersion_results Purpose: Detect posts being quoted at statistically anomalous rates — potential targets of coordinated quote-post campaigns.

Same statistical approach as URL overdispersion but applied to quote-posts. Tracks by quoted_uri (AT-URI) and quoted_author_did. Produces both hourly and daily results.

Key columns: quoted_uri, quoted_author_did, granularity, total_shares, unique_sharers, sharer_density, volume_p_value, density_p_value, is_anomaly, baseline_source, sample_dids.

PDS Signup Anomaly Sidecar

Table: pds_signup_anomalies Purpose: Detect unusual PDS signup patterns by host using Poisson models.

Monitors signup rates per PDS host at daily and hourly granularity. Flags when observed signup count is statistically unlikely given the baseline rate. Excludes known high-volume hosts (bsky.network, bridgy-fed, mostr.pub).

Key columns: pds_host, granularity, observed_count, distinct_accounts, expected_lambda, p_value, is_anomaly, baseline_source, dispersion_index, rolling_mean, rolling_variance, sample_dids.

How It Works

1. Event Stream: The AT Protocol firehose emits events (new posts, profile updates, follows, etc.)
2. Rule Evaluation: Osprey evaluates all rules and models against each event
3. Result Recording: Osprey writes a row to osprey_execution_results with system columns (__action_id, __timestamp, etc.) and populates each rule/model's column with its result (1/0 for rules, scores for models, strings for extractors). Columns for rules that didn't evaluate remain NULL.
4. Data Availability: Investigators and moderators query ClickHouse to understand which accounts are triggering which rules

ClickHouse Data Access

Connection

The MCP server connects directly to a ClickHouse server. Requires:

• Host and port of the ClickHouse server
• Username and password
• Network access to the server

Connection details load from the project .envrc via direnv (CLICKHOUSE_PASSWORD from secrets/clickhouse.env); the MCP server inherits them at startup. Do not print secret values.

Queryable Tables

Table	Source	Purpose
default.osprey_execution_results	Osprey rule engine	Rule execution history
default.pds_signup_anomalies	Signup anomaly sidecar	PDS signup rate anomalies
default.url_overdispersion_results	URL overdispersion sidecar	Coordinated domain sharing anomalies
default.account_entropy_results	Account entropy sidecar	Bot-like posting pattern detection
default.url_cosharing_pairs	URL co-sharing sidecar	Daily URL co-sharing pairs (TTL 7 days)
default.url_cosharing_clusters	URL co-sharing sidecar	URL cluster metrics and evolution (no TTL)
default.url_cosharing_membership	URL co-sharing sidecar	Daily URL cluster membership (TTL 7 days)
default.quote_cosharing_pairs	Quote co-sharing sidecar	Daily quote co-sharing pairs (TTL 7 days)
default.quote_cosharing_clusters	Quote co-sharing sidecar	Quote cluster metrics and evolution (no TTL)
default.quote_cosharing_membership	Quote co-sharing sidecar	Daily quote cluster membership (TTL 7 days)
default.quote_overdispersion_results	Quote overdispersion sidecar	Coordinated quote-post anomalies

All tables are read-only. The MCP server enforces:

• SELECT/WITH only — No INSERT, UPDATE, DELETE, DDL
• LIMIT required — All queries must have a LIMIT clause
• No semicolons — Multi-statement execution not allowed
• No INTO — Data export not allowed
• Timeout — Queries that run longer than 60 seconds are cancelled

JOINs, UNIONs, CTEs, subqueries, and any table are allowed. These constraints are enforced at the MCP layer before queries reach ClickHouse.

Query Tool

Use the clickhouse_schema MCP tool to get column metadata:

Tool: clickhouse_schema
Purpose: Return column names and types for osprey_execution_results

Use the clickhouse_query MCP tool to execute SELECT queries:

Tool: clickhouse_query
Parameters:
  query: SELECT ... FROM default.osprey_execution_results WHERE ... LIMIT ...
Purpose: Execute read-only queries, return results as JSON

Relationship to Ozone

Ozone is the labelling system for the AT Protocol. It allows moderators to apply labels to accounts, posts, and other objects.

Osprey → Ozone flow:

1. Osprey rule detects problematic content (rule matches)
2. Investigator reviews Osprey data via ClickHouse queries
3. Investigator uses the ozone_label MCP tool to apply a label
4. Ozone records the label, which may affect visibility/filtering of that content

Osprey data informs labelling decisions, but the two are separate systems:

• Osprey is automated detection
• Ozone is manual labelling (though it can be automated via orchestration)

Relationship to osprey-rules Plugin

The osprey-rules plugin is for writing rules (authoring SML).

This skill is for accessing and querying rule execution data (understanding results).

If you need to:

• Write a new rule → Use osprey-rules plugin and authoring-osprey-rules skill
• Review/debug a rule → Use osprey-rules plugin and reviewing-osprey-rules skill
• Query rule results → Use this skill and querying-clickhouse skill

Schema Reference

For the complete column listing, column types, and semantic descriptions, see:

references/osprey-schema.md — Full schema documentation

System columns (present on every row):

• __action_id — Unique evaluation event identifier (Int64)
• __timestamp — When the evaluation occurred, UTC (DateTime64(3))
• __error_count — Errors during evaluation (Nullable(Int32))
• __atproto_label — Labels applied (Array(String))
• __entity_label_mutations — Label changes applied (Array(String))
• __verdicts — Verdict strings emitted by rules (Array(String))

Common dynamic columns (PascalCase, all Nullable):

• ActionName — AT Protocol action type (e.g., create_post, create_follow)
• AccountAgeSeconds — Account age in seconds at evaluation time
• DisplayName — Account display name
• PostHasExternal — Whether post contains an external link
• Rule columns (e.g., AltGovHandleRule) — UInt8, 1 = matched
• Score columns (e.g., ToxicityScoreUnwrapped) — Float64

Common Investigation Patterns

Investigation queries usually follow these patterns:

Find accounts matching a specific rule:

SELECT __action_id, __timestamp, DisplayName, AccountAgeSeconds
FROM default.osprey_execution_results
WHERE AltGovHandleRule = 1
  AND __timestamp > now() - INTERVAL 7 DAY
LIMIT 100

Count rule hits over time:

SELECT
    toDate(__timestamp) AS day,
    countIf(AltGovHandleRule = 1) AS alt_gov_hits,
    countIf(DigestRepostBotRule = 1) AS digest_bot_hits
FROM default.osprey_execution_results
WHERE __timestamp > now() - INTERVAL 7 DAY
GROUP BY day
ORDER BY day
LIMIT 30

Check multiple rules for recent activity:

SELECT __timestamp, AltGovHandleRule, SuicidalContentRule, DigestRepostBotRule
FROM default.osprey_execution_results
WHERE ActionName = 'create_post'
  AND __timestamp > now() - INTERVAL 1 DAY
LIMIT 100

For proven query patterns, see the querying-clickhouse skill.

Performance Tips

1. Always filter on __timestamp — this is the partitioning key and critical for performance
2. Use LIMIT — results can be large; always limit rows
3. Select specific columns — with 600+ columns, SELECT * is extremely expensive. ClickHouse is column-oriented, so fewer columns = faster queries
4. Dynamic columns are sparse — most rule columns are NULL for any given row; only select the rules you care about
5. No rule_name column — each rule is its own column. Query specific rules by column name, not by filtering a generic field

Next Steps

• Read references/osprey-schema.md to understand all available columns
• Load the querying-clickhouse skill to learn 15+ proven query patterns
• Use the clickhouse_query MCP tool to execute exploratory queries