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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false. The description adds valuable behavioral context beyond these: it explains scoping to the agent's identifier (anonymous IP, BYO key hash, or account ID) and the dual behavior of retrieving vs listing. No contradiction with annotations.

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, each earning its place: function, use cases, and scope/relationship. No filler, front-loaded with the core 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 tool with one optional parameter and no output schema, the description fully covers what it does, when to use it, scoping rules, and its relationship to siblings. It hints at return values ('Retrieve a value' / 'list all saved keys'), which is sufficient given the absence of an output schema.

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%, so the baseline is 3. The description reinforces the parameter semantics by explaining that 'key' refers to a value previously saved via 'remember' and reiterates that omitting it lists all keys. This adds meaning beyond the schema's terse 'omit to list all keys'.

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'), and explicitly distinguishes the two modes: retrieving a value or listing all keys. It also differentiates from siblings by naming 'remember' and 'forget' as the save/delete counterparts.

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?

Provides clear context for when to use the tool ('to look up context the agent stored earlier... without re-deriving it from scratch') and explicitly names alternatives for related operations: 'Pair with remember to save, forget to delete.' This gives the agent actionable guidance on tool selection.

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