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

Beyond the annotations (idempotentHint, readOnlyHint, destructiveHint), the description discloses important behavioral traits: the memory is scoped by identifier, authenticated users get persistent memory, and anonymous sessions retain memory for only 24 hours. It does not explicitly mention what happens on overwriting an existing key, but the idempotent hint covers some of that context.

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 compact and well-structured: it opens with the core action, gives use-case examples, then explains scoping and retention, and ends with companion tools. Every sentence earns its place without unnecessary repetition or fluff.

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 two-parameter save operation with no output schema, the description covers the essential operational context: what to save, when to use it, how long it persists, and how it relates to recall/forget. It does not describe return values or error behavior, but those are not critical for invoking this tool effectively.

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?

The input schema already describes both parameters (key and value) with 100% coverage, including examples for keys and the note that value can be any text. The description adds minimal extra parameter meaning, so it stays at the baseline for high schema coverage.

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 a specific verb and object: 'Save data the agent will need to reuse later.' It also identifies this as a key-value memory store and differentiates it from sibling tools by explicitly referencing recall and forget, making its purpose unmistakable.

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 provides explicit usage guidance with concrete examples: 'Use when you discover something worth carrying forward (a resolved ticker, a target address, a user preference, a research subject).' It also explains the pairing with recall and forget, which serves as an alternative/companion tool reference.

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