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

Beyond the annotations (idempotentHint=true, destructiveHint=false), the description adds critical behavioral detail: 'Stored as a key-value pair scoped by your identifier. Authenticated users get persistent memory; anonymous sessions retain memory for 24 hours.' This explains scoping and retention semantics, which are not conveyed by the annotations. No contradiction with annotations.

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 adding distinct value: purpose, usage trigger, storage semantics, and companion tools. It is front-loaded with the primary action and includes no filler or redundant information. Every sentence 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 2-parameter write tool with no output schema, the description covers purpose, usage context, persistence rules, scoping, and companion tools. Annotations handle safety (idempotent, non-destructive). The description is complete enough for an agent to correctly select and invoke the tool without ambiguity.

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 described with examples), so baseline is 3. The description adds meaning by explaining the key-value pair model, scoping by identifier (key uniqueness per user), and providing domain examples for values ('findings, addresses, preferences, notes'). This clarifies how to choose keys and values, going slightly beyond the schema.

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 function: 'Save data the agent will need to reuse later — across this conversation or across sessions.' It uses a specific verb ('save') and resource ('data' as key-value pair), and distinguishes from siblings by explicitly pairing with 'recall' (retrieve) and 'forget' (delete), making its unique role 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 provides explicit when-to-use guidance with concrete examples: 'Use when you discover something worth carrying forward (a resolved ticker, a target address, a user preference, a research subject) so you don't have to look it up again.' It also differentiates from recall and forget by stating 'Pair with recall to retrieve later, forget to delete,' and clarifies persistence context (authenticated vs anonymous) that affects when memory is reliable.

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