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

Annotations already set idempotentHint=true, readOnlyHint=false, and destructiveHint=false. The description adds meaningful behavior beyond this: persistence across sessions vs. 24-hour anonymous retention, key-value scoping by identifier, and authentication-dependent lifetime. It does not mention overwrite semantics on duplicate keys, which would be valuable, but the provided context is solid.

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 four sentences but each earns its place: purpose, use cases, storage model, persistence semantics, and companion tools. It is front-loaded with the action and avoids filler.

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 2-param tool with no output schema, the description covers purpose, usage cues, persistence details, and related tools. Missing details like overwrite behavior or key constraints are minor for this tool class. The annotation hints plus description make the tool ready for correct invocation.

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 coverage is 100%: both 'key' and 'value' are described with examples. The description adds little beyond schema, just 'key-value pair' and general examples already in the schema. Baseline 3 is appropriate because the schema does the heavy lifting.

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 opens with a specific verb+resource: 'Save data the agent will need to reuse later,' then gives concrete examples (ticker, address, user preference) and clearly distinguishes from siblings (recall, forget) by explicitly naming them.

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?

Provides explicit when-to-use guidance: 'Use when you discover something worth carrying forward' and lists example triggers. It also names alternatives/companion tools ('Pair with recall to retrieve later, forget to delete'), making the decision context clear.

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