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

Annotations already indicate the tool is non-read-only, idempotent, and non-destructive. The description adds valuable behavioral context: key-value scoping by identifier, persistence differences between authenticated and anonymous sessions, and the 24-hour retention for anonymous sessions. It does not contradict annotations, and the additional context goes beyond what annotations provide.

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 a compact three sentences, front-loaded with purpose and followed by usage and behavior. Each sentence contributes useful information without redundancy. Slightly longer than strictly necessary, but all content earns its place.

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 memory-write tool with two required parameters and no output schema, the description covers essential context: what to store, when to use, how data is scoped/persisted, and lifecycle (pairing with recall/forget). No critical gaps remain.

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 descriptions cover 100% of parameters with clear examples for key and value. The description reinforces the key-value nature but does not add meaning beyond the schema. Since schema coverage is high, the baseline of 3 applies, and the description does not need to compensate.

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') and clearly distinguishes from siblings by naming complementary tools (recall, forget). It also clarifies scope (conversation or sessions) and value examples, leaving no ambiguity about the tool's function.

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?

It explicitly states when to use the tool ('Use when you discover something worth carrying forward') with concrete examples, and also mentions pairing with recall and forget. This gives clear guidance on usage and alternatives, satisfying the 'when-to-use vs alternatives' criterion.

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