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

Annotations already provide readOnlyHint=false, idempotentHint=false, and destructiveHint=false. The description adds useful behavioral context beyond those: this persists across sessions and is meant for durable facts rather than ephemeral or transcript-style data. It does not detail duplicate-handling or overwrite behavior, but the idempotency annotation partially covers that.

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?

Three sentences, each earning its place: the core behavior, the when-to-use guidance, and the explicit anti-pattern. The most important information is front-loaded in the first sentence.

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 3-parameter write tool with a rich schema and an output schema present, the description provides complete selection and usage context. Nothing essential is missing for an agent to decide whether and how to invoke it.

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 100%, and each parameter (text, metadata, namespace) has a detailed description including namespace format constraints and metadata examples. The description itself adds no parameter-level semantics, so the baseline 3 is appropriate: the schema carries the burden, 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 and resource: 'Store a durable fact, preference, or decision into persistent memory across sessions.' It clearly differentiates from sibling read tools like recall and recent_memories by framing this as the write operation for durable knowledge.

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 gives explicit positive guidance ('Use when you discover an important user preference, key background detail, architecture choice, or durable fact') and explicit negative guidance ('Do NOT use for storing entire conversation logs or transient temporary state'). This strongly steers an agent toward correct selection even without naming sibling alternatives.

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