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

Annotations already declare safe read-only idempotent behavior. Description adds scoping detail (by identifier) and the alternative behavior (omit key to list all), providing context beyond annotations without 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?

Three sentences efficiently cover purpose, use case, and scoping. Front-loaded with the primary action. The pairing note is helpful but slightly redundant with sibling awareness.

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 retrieval tool with one optional parameter and no output schema, the description covers behavior, scope, and usage. Lacks explicit mention of error handling if key not found, but overall adequate.

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 covers 100% of parameters with description matching. The free-text description reiterates the listing behavior and provides examples (ticker, address), adding marginal value but not surpassing baseline given full 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?

Clearly states it retrieves a value by key or lists all keys when omitted. Distinguishes from siblings by explicitly mentioning partners `remember` and `forget`, and provides concrete examples of usage contexts (ticker, address, notes).

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?

Gives specific use cases (look up stored context) and explains how to list keys by omitting the argument. Does not explicitly state when not to use, but the context is clear and alternatives among siblings are not required due to specificity.

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