Conciseness

Every line is an operational rule or navigation, not explanation: "Resolve replies and forwards with a message ID. Never pass a thread ID where a message ID is required" and "Do not invent recipients, attachments, claims, signatures, or commitments" assume Claude's competence and add only domain-specific contracts. Not 4 because there is no tutorial content, no concept explanation, and no padding to trim — the one apparent overlap (step 5's confirmation rule vs. the matrix's "Preview + confirm" row) is workflow-vs-policy emphasis covering different trigger sets, not redundancy.

Actionability

The body names exact commands for every operation — "Use `create_draft` for review or scheduled delivery, `send_draft` for an approved draft, `send_message` for new mail, `reply_to_message` for replies, and `forward_message` for forwards" plus `list_inboxes` and `get_thread` — and prescribes exact outputs ("Return the message and thread IDs, or the draft ID and scheduled time"). Not 4 because the verb-to-tool mapping covers all common cases with explicit decision rules, leaving no gaps an instruction-only skill needs code to fill; guidance is fully executable without guessing.

Workflow Clarity

The 7-step "Execute safely" sequence is explicit with validation checkpoints and an error-recovery loop: branch on ambiguity ("If multiple candidates remain or listing is unavailable, ask for the exact sender inbox"), a confirmation gate ("If any externally visible field was inferred, show the complete sender, recipients, subject, body, attachments, and action, then request confirmation before sending"), and retry reconciliation ("Do not retry a send after an ambiguous timeout without checking whether the message was created"), reinforced by the matrix's preview-and-confirm triggers for sensitive/legal/financial/bulk/BCC/reply-all/external risk. Not 4 because checkpoints are explicit rather than implicit and the timeout-recovery feedback loop is present, so neither the anchor-4 "minor validation gaps" nor the missing-validation cap at 3 applies.

Progressive Disclosure

The body is under 50 lines with no bundle files of its own, well-organized into four clear sections, and delegates deep material via a clearly signaled one-level reference: "The full matrix and threat model live in the `agent-email-patterns` skill (`references/threat-model.md`); the rows below are this skill's contract." Not 4 because nothing that belongs in a separate file is inlined (the 4-row matrix kept inline is the operative contract), the external reference is explicit with skill name and path, and per the simple-skill exception well-organized sections suffice for a skill with no external bundle.

Specificity

The description lists multiple concrete actions covering the domain comprehensively: "Draft, send, reply to, or forward email through the connected AgentMail MCP server" plus "compose messages, create or schedule drafts for review, or send to named recipients" — seven distinct operations, matching the anchor example's breadth ("Extract text and tables from PDF files, fill forms, merge documents, convert pages to images"). Not 4 because there are no minor gaps in coverage: drafting, sending, replying, forwarding, scheduling, and recipient handling are all explicitly named, and the mechanism (AgentMail MCP server) is stated.

Completeness

Both questions are explicitly answered with concrete trigger phrases: what — "Draft, send, reply to, or forward email through the connected AgentMail MCP server"; when — "Use for ANY request to send, reply to, or forward mail — even a quick one-line send" and "Also use to compose messages, create or schedule drafts for review, or send to named recipients." Not 4 because the "when" is not merely present but explicit and specific, exceeding the anchor-4 example ("Use when working with PDF files") and matching the anchor-5 example's structure, with negative triggers adding further precision.

Trigger Term Quality

Natural user vocabulary is comprehensively covered with synonyms: "email" and "mail", "send", "reply to", "forward", "compose", "draft", "schedule", "named recipients" — the full set of phrases a user would naturally say when needing this skill. Not 4 because no common natural terms are missing for this domain (file extensions are inapplicable to email); both "email" and "mail" variants appear alongside all operation verbs.

Distinctiveness Conflict Risk

The niche is clear (outbound mail via AgentMail) and the description actively routes away from siblings: "do not use for reading or triaging mail (agentmail-check-email), inbox administration (agentmail-manage-inboxes), or MCP connection setup (agentmail-mcp)" — naming the three adjacent skills explicitly. Not 4 because conflict risk is minimal, going beyond the anchor-5 example by including explicit negative boundary triggers rather than merely distinct positive ones.