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

Annotations declare readOnlyHint, idempotentHint, and destructiveHint, but the description adds meaningful behavioral context beyond these: scoping to the user's identifier (anonymous IP, BYO key hash, or account ID) and the dual-mode behavior (retrieve single value vs. list all keys). This goes beyond the annotations and enriches the agent's 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?

Two sentences, front-loaded with the primary action, then usage guidance and scoping. Every word earns its place; there is no fluff or repetition of schema content.

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 tool with one optional parameter, the description covers purpose, usage, scoping, and sibling relationships. It explicitly states the two invocation modes (with and without key). The lack of an output schema is not a gap because the return behavior is implied clearly ('retrieve a value' or 'list keys').

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 schema already covers the single 'key' parameter with a description, so baseline is 3. The description adds semantic richness by explaining the 'omit to list' behavior in the first sentence and providing concrete examples of stored values (ticker, address, research notes), which helps the agent map intent to the parameter without adding bulk.

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 opens with a clear, specific verb and resource: 'Retrieve a value previously saved via remember, or list all saved keys.' It distinguishes from sibling tools (remember, forget) by explicitly framing recall as the retrieval counterpart, so there is no ambiguity about its 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?

It provides explicit when-to-use guidance: 'Use to look up context the agent stored earlier... without re-deriving it from scratch.' It also names the paired tools (remember, forget) and their relationship, giving clear context for when to use recall versus the alternatives.

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