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

Annotations already declare the tool as read-only and non-destructive, but the description goes beyond this by revealing scoping behavior ('Scoped to your identifier (anonymous IP, BYO key hash, or account ID)') and the ability to list all keys. These are meaningful contextual details that annotations do not capture, providing the agent with essential behavioral understanding.

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 concise (three sentences) and front-loaded with the primary function. Each sentence earns its place: the first states the core operation, the second provides usage context and examples, and the third explains scoping and complementing tools. No wasted words or redundant restatement of schema fields.

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 the tool's simplicity (one optional parameter, no output schema, strong annotations), the description is remarkably complete. It covers behavior (retrieve/list), usage rationale (avoid re-deriving), scoping, and integration with siblings. The only potential omission is error behavior for missing keys, but this is mitigated by the absence of an output schema and the tool's read-only nature.

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% (the 'key' parameter is fully described in the schema). The description adds value by elaborating on what kinds of keys might be stored ('the user's target ticker, an address, prior research notes'), giving the agent concrete expectations for parameter values beyond the schema's brief definition.

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 uses a specific verb ('Retrieve') and resource ('a value previously saved via remember'), clearly distinguishing the tool from siblings like remember (save) and forget (delete). It also explicitly states the alternate behavior of listing all keys when the key is omitted, leaving no ambiguity about its primary function.

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: 'Use to look up context the agent stored earlier — the user's target ticker, an address, prior research notes — without re-deriving it from scratch.' It also references sibling tools for complementary operations ('Pair with remember to save, forget to delete'), indicating the intended workflow and implicitly excluding itself from saving/deleting.

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