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

Adds significant behavioral context beyond annotations: scoped by identifier, persistent for authenticated users, 24-hour retention for anonymous, and pairing with recall/forget. Annotations only provide idempotentHint=true and write/not-destructive hints.

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?

Four sentences, all informative but slightly verbose. Could be tightened without losing meaning. However, it is well-structured and front-loaded with the core purpose.

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?

Given no output schema and two required parameters, description fully covers what the agent needs: purpose, when to use, parameter semantics, persistence behavior, and sibling relationships. No 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 already covers parameters with good descriptions (100% coverage). Description adds value by giving concrete examples (e.g., 'subject_property', 'target_ticker') and emphasizing the key-value nature, going 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?

Description clearly states the verb 'Save data' and the resource 'key-value pair' for reuse across sessions, and distinguishes from siblings 'recall' and 'forget' by explicitly mentioning them.

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?

Explicitly provides when to use (when discovering something worth carrying forward) and offers clear context with exclusions (anonymous session memory limit) and alternatives (recall, forget).

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