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

Annotations indicate idempotentHint=true and destructiveHint=false. The description adds valuable context: memory is scoped by identifier, persistent for authenticated users, and 24-hour retention for anonymous sessions. This goes beyond what annotations provide, though it could potentially mention that idempotent means re-saving same key updates value.

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, each with clear purpose. The first sentence states the main action, the second explains when to use, the third details storage mechanics, and the fourth references sibling tools. No superfluous words.

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 the tool has only 2 required parameters and no output schema, the description fully addresses usage: what to store, when, how it's scoped, retention policy, and pairing with recall/forget. No gaps remain for typical use cases.

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%, so baseline is 3. The description adds examples for key (e.g., 'subject_property') and clarifies value can be 'any text'. This adds meaning beyond the schema's dry descriptions, earning a 4.

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's purpose: 'Save data the agent will need to reuse later'. It uses a specific verb (save) and resource (data), and distinguishes from sibling tools like recall and forget by explicitly pairing with 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?

The description provides explicit guidance on when to use the tool: 'Use when you discover something worth carrying forward'. It also mentions pairing with recall and forget, giving context on lifecycle. However, it does not explicitly state when not to use it, so a small deduction applies.

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