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

Annotations declare readOnlyHint=false and destructiveHint=false, so the safety profile is already covered. The description does add genuine value beyond that: values are size-limited and content is screened for PII. However, it says nothing about overwrite semantics or what happens when the TTL expires.

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?

Two short sentences with zero waste; the storage constraint is front-loaded ahead of the validation caveat. Nothing could be cut without losing information.

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?

For a three-parameter write tool with no output schema and no parameter descriptions, the definition does too little: the size limit for 'small', overwrite behavior, and error conditions on PII rejection are all unspecified.

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?

Schema description coverage is 0%, so all three required parameters (key, value, ttl_s) are undocumented by the schema. The description gestures at 'value' and TTL but never quantifies 'small', gives no unit or bounds for ttl_s beyond the schema's integer constraint, and says nothing about key format.

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 verb and resource (write a value into the key-value store) plus the defining constraint (TTL, small values). It is clearly distinguishable from kv.get and kv.delete, though it doesn't explicitly name those siblings.

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?

The only guidance is a negative constraint (emails and card numbers are rejected); there is no statement of when to use this over idem.begin or timer.set, nor any prerequisites. Usage must be inferred from the name alone.

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