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

The annotations already indicate readOnlyHint=false, idempotentHint=true, and destructiveHint=false. The description adds valuable behavioral context: storage as a key-value pair scoped by identifier, and persistence semantics (persistent for authenticated users, 24-hour retention for anonymous). This goes beyond the structured annotations and shows no contradiction.

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 serving a distinct purpose: purpose, usage timing, storage/retention, and companion tools. No unnecessary words or repetition. Front-loaded with the primary action.

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 key-value store with no output schema, the description covers purpose, usage, persistence, and complementary operations. It also explains the scoped and TTL behavior, which is crucial for the agent. No gaps for the tool's complexity.

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 fully describes both parameters with 100% coverage, so baseline is 3. The description's reference to 'key-value pair' and examples of values aligns with the schema but adds no new parameter-specific semantics. The scoping detail is a behavioral trait, not parameter meaning.

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 ('Save') and resource ('data the agent will need to reuse later'), and explicitly distinguishes itself from siblings by mentioning 'Pair with recall to retrieve later, forget to delete.' Examples like 'a resolved ticker, a target address' further clarify its purpose.

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...' and provides concrete scenarios. It also names complementary tools (recall, forget), giving the agent guidance on alternatives. No explicit exclusions, but the guidance is clear.

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