Conciseness

The body is lean and tool-focused, but the table's "Why" column ("balanced stability", "mismatched Tm → one primer anneals poorly", "long enough for specificity, short enough for efficient annealing") restates standard molecular biology Claude already knows, fitting the 4 anchor (efficient with minor over-explanation that could be trimmed). It is not 5 because trimming the Why column to property+target would lose nothing Claude can't supply; it is well above 3 since there is no padded prose or concept introduction.

Actionability

The two main workflows are copy-paste-ready `tu run` commands with realistic parameter values, and tool parameters for IDT/NEB are named inline. It falls short of the 5 anchor because `scripts/primer_qc.py` — presented as the QC mechanism "for primers from any source" — has no invocation example, and `IDT_analyze_oligo` / `DNA_calculate_gc_content` are described but never shown as commands.

Workflow Clarity

Steps 1–5 are clearly sequenced (design → Tm/Ta → QC rules → specificity → gotchas) with a genuine feedback loop: the constraint-quirk block quotes the literal error messages ("Target region (N bp) is smaller than product_size_min") and maps each to a specific fix, and Step 4 is an explicit validation checkpoint ("confirm a single intended product before ordering"). It is not 4 because both error-recovery guidance and pre-order validation checkpoints are explicit, not merely implied.

Progressive Disclosure

The body is a well-organized ~73-line overview whose only bundle reference, `scripts/primer_qc.py`, is real (verified present in scripts/), clearly signaled, and one level deep — matching the 5 anchor of well-signaled one-level-deep references with content appropriately kept inline at this scale. There are no buried or nested references.

Specificity

The description lists five concrete, distinct actions — "design forward/reverse primers for a target region", "compute melting temperature (Tm) and annealing temperature (Ta)", "check GC content", "screen an oligo for hairpins and primer-dimers", and covering design rules — which is comprehensive coverage, matching the 5 anchor. It exceeds the 4 anchor ("several specific actions; minor gaps") because no core capability of the skill is missing.

Completeness

Both questions are answered explicitly: the "what" is the enumerated action list, and the "when" is a concrete trigger clause — "Use when you need primers for a sequence, want to QC an existing primer pair, or need the Tm of an oligo." This matches the 5 anchor verbatim in structure; the 4 anchor's weaker 'when could be more explicit' does not apply.

Trigger Term Quality

Natural terms and synonyms are comprehensive: "PCR / qPCR", "primer", "oligo", "Tm", "annealing temperature", "GC content", "hairpins", "primer-dimers", "QC an existing primer pair" — exactly the phrases a user would say. It fits the 5 anchor (comprehensive natural terms with synonyms; no file extensions are relevant to this domain, so their absence is not a gap).

Distinctiveness Conflict Risk

It occupies a clear niche (PCR/qPCR primer and oligo design with named thermodynamic methods and tools) with triggers unlikely to fire for unrelated skills. It is not the 4 anchor because there is no meaningful overlap with a closely related skill — "need the Tm of an oligo" or "QC a primer pair" would not plausibly route to a generic sequence-analysis or document skill.