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

The annotations already indicate this is a write (readOnlyHint=false) and idempotent tool. The description adds valuable context beyond annotations, including scoping by identifier, persistent vs. 24-hour retention for authenticated vs. anonymous sessions. It does not contradict the annotations and provides useful behavioral details, though some aspects (e.g., overwrite behavior) are not explicitly stated.

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?

The description is concise and well-structured, front-loaded with the main purpose followed by usage context, storage details, and related tools. Every sentence adds value without redundancy, and the length is appropriate for the tool's simplicity.

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 simple two-parameter set operation, the description is fairly complete: it explains what, when, how, and persistence. It does not explain return values, but that is acceptable given no output schema and the tool's basic nature. Minor omissions like key size limits or overwrite semantics are not critical for a tool of this simplicity.

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?

The input schema covers both parameters (key and value) with descriptive text and examples, achieving 100% coverage. The description adds little beyond the schema, merely restating that it stores a key-value pair. Per the rubric, high schema coverage warrants a baseline score of 3, and the description does not significantly enhance parameter understanding.

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?

The description clearly states the tool saves data for later reuse, with a specific verb ('Save') and resource ('data'), and provides concrete examples (resolved ticker, target address). It distinguishes itself from sibling tools by mentioning the key-value pair mechanism and explicitly pairing with recall/forget, making its purpose unambiguous.

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 description gives explicit guidance on when to use the tool ('Use when you discover something worth carrying forward... so you don't have to look it up again') and mentions the companion tools recall and forget. However, it does not explicitly state when not to use it or provide exclusions, so it stops short of a perfect score.

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