Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnly/idempotent/non-destructive, so safety is covered. The description adds non-obvious behavioral context: the summary is rewritten only when indicators change, and it discloses that stale/ageDays fields exist. It does not describe the output shape, which is reasonable given no output schema exists, but leaves some ambiguity.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loads purpose and then adds interpretation guidance. Slightly longer than a minimal definition, but each sentence (especially the risk-scale explanation) earns its place because it changes how an agent interprets the score.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given zero params, no output schema, and rich annotations, the description is essentially complete: it explains what the tool returns conceptually, how to detect staleness, and how to interpret the score range. Minor gap is the exact structure of the returned summary.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Zero parameters, so baseline is 4. The description appropriately focuses on return-value semantics (score, regime, stale, ageDays) rather than parameters, which is correct for a no-arg tool.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific resource (the latest written summary of the Zensei Index) and what it contains (score and regime). It distinguishes itself from zensei_index_today by noting it is the 'written summary' rather than the current number, though the boundary is soft.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explicitly says to check `stale` and `ageDays` before quoting, and to prefer zensei_index_today for the current number. This names the alternative and the condition that selects it.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.