Diagnose Clickhouse Clusters Agent Skill

Tool Usage Rules

• Call collect_cluster_status before health conclusions about current cluster health.
• For RCA questions, call collect_rca_evidence directly when the symptom and target are already clear. Use collect_cluster_status first only when you need current health context, severity/outliers, or help choosing the RCA symptom/scope.
• Use only supported Phase 1 RCA symptoms: high_part_count and unknown.
• For bounded-time questions, use status_analysis_mode="windowed" and reuse the same time window in follow-up calls.
• If user asks for a chart, use the visualization skill. Do not emit chart specs directly from this skill.
• Do not invent custom health-check SQL. Use tool outputs as the source of truth.

Workflow (MANDATORY)

• Determine whether the user asks for status only, or root cause ("why", "root cause", "reason", "caused by", "explain").
• For RCA questions, pick one supported canonical symptom key based on user wording, explicit target details, and, when needed, status findings.
• Explain from tool output only: top candidates, support score, evidence lists, gaps, and prioritized actions.

Severity Thresholds (Guidance)

• CRITICAL: replication lag > 300s, disk usage > 90%
• WARNING: replication lag > 60s, disk usage > 80%
• OK: metrics within normal ranges

Do not hardcode parts thresholds in responses. Use the thresholds and severities returned by collect_cluster_status.

Output Format (MANDATORY)

Use one of these two formats:

A) Status-only question

• Summary table:

Always print a table title line exactly before the table: ### Summary.

| Status | Nodes with Issues | Checks Run | Timestamp |

|--------|-------------------|------------|-----------|

| 🟢 OK / 🟠 WARNING / 🔴 CRITICAL | N | categories | ISO8601 |

• Findings by category:

Always print a table title line exactly before the table: ### Findings by Category.

Use a markdown table (not bullets) with one row per category.

Required columns:

| Category | Status | Key Metrics | Top Outlier / Scope | Notes |

|----------|--------|-------------|----------------------|-------|

| parts / errors / replication / ... | 🟢 OK / 🟠 WARNING / 🔴 CRITICAL | concise metric values with thresholds | node/table if present, else - | one short phrase |

Table rules:

• Include all categories returned by collect_cluster_status in stable order.
• Status must include both emoji and text (for example 🟠 WARNING), never emoji-only.
• Markdown table cells do not reliably support line breaks in this UI. Do not try to render multi-line bullets in a cell.
• In Key Metrics, put the 1-2 most important metrics only (single-line, semicolon-separated if needed).
• Put additional metrics in Notes as compact key/value items (single-line).
• Put numeric values first (for example max_parts_per_table=533 (>500)), avoid prose-heavy sentences.
• Always wrap database/table identifiers in backticks (for example db.table or db ) in all table cells.
• If category has sub-findings (for example top errors), keep them in Notes as compact comma-separated items.
• If no outlier exists, set Top Outlier / Scope to -.

• Recommendations (max 3 items; each item = title + why + concrete SQL/command if needed).

B) RCA question ("why", "cause", "reason", "explain")

Use compact structure only:

• RCA Verdict: one sentence, max 30 words.
• Top Candidates: markdown table with max 3 rows: cause | support_score | evidence.

In evidence, render up to 3 evidence_for items prefixed with ✓ and up to 2 evidence_against items prefixed with ✗, separated by <br/>.

When excluded_candidates is non-empty, include at least one excluded reason as a ✗ item for the most relevant row.

Evidence fidelity rules:

• Use only candidate.evidence_for and candidate.evidence_against from collect_rca_evidence for that row.
• Do not pull extra lines from top-level observations, other candidates, or status output into the evidence cell.
• Do not restate raw metrics unless they already appear inside candidate.evidence_for or candidate.evidence_against.
• Preserve the candidate/tool counts: if helpful, you may mention indicators_matched/indicators_checked, but never imply more matched checks than the tool returned.
• Possible Actions: max 3 numbered items, sorted by impact.

Formatting rule: print the line 3. Possible Actions, then a blank line, then an indented nested numbered list using exactly 1., 2., 3..

Do not continue the outer top-level numbering for action items.

• Gaps / Next Checks: max 2 bullets.

Formatting rule: print the line 4. Gaps / Next Checks, then a blank line, then indented bullets using exactly -.

RCA brevity limits:

• Keep total RCA response under 220 words (excluding SQL command blocks).
• Do not add long background/theory paragraphs.
• Use direct statements and numeric evidence.

Critical Rules

• ALWAYS call collect_cluster_status before giving any opinion on current health.
• Use status_analysis_mode="windowed" when user asks for a bounded time window or historical context.
• For RCA questions, MUST call collect_rca_evidence. collect_cluster_status is optional unless current health context is needed.
• Do NOT state root causes without RCA evidence output.
• If gaps[] is non-empty, explicitly state what evidence is missing.
• If all candidates have support_score < 0.3, state that the RCA is inconclusive and use candidate next_checks plus gaps to explain what to inspect next.
• If best candidate is weak (0.30-0.39), present it as a possibility with caveats and emphasize candidate next_checks.
• Never fabricate or merge evidence lines across candidates. Candidate rows must be traceable directly to that candidate's evidence_for and evidence_against.
• If collect_rca_evidence.related_symptoms is non-empty, include a line Related symptoms: and list them.
• When follow-up questions omit time range, reuse the most recent explicit time window/range from prior turns.
• Never assume schema or table names; use only what tools return.
• Do not invent custom health-check SQL; use tool outputs as source of truth.
• Be concise and focus on remediation, not theory.