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

Annotations already mark it readOnly and idempotent. The description adds valuable context about scoping: 'Scoped to your identifier (anonymous IP, BYO key hash, or account ID),' which goes beyond annotations. It also clarifies the dual mode of behavior.

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 three well-structured sentences with no filler. The main action is front-loaded in the first sentence, and scoping and companion tools are efficiently mentioned without redundancy.

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?

The description covers purpose, usage, scoping, and companion tools, which is complete for a simple tool with one optional parameter. It does not mention behavior for missing keys, but given the annotations and schema, this is a minor gap.

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 input schema fully describes the single optional 'key' parameter with 100% coverage. The description echoes this behavior ('omit the key argument') and adds the connection to 'remember,' but it doesn't add substantial new semantic meaning beyond what the schema already provides.

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 clearly states 'Retrieve a value previously saved via remember, or list all saved keys (omit the key argument),' which is a specific verb+resource. It also distinguishes from sibling tools by naming remember and forget and their roles.

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 explicitly says 'Use to look up context the agent stored earlier' and provides concrete examples like 'user's target ticker, an address, prior research notes.' It also names alternatives by saying 'Pair with remember to save, forget to delete.'

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