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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint. The description adds valuable behavioral context: scoping to the user's identifier (anonymous IP, BYO key hash, or account ID) and the ability to list all keys by omitting the argument. No contradictions.

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, no wasted words. Front-loaded with the core function, then use cases, then scoping and pairing. Every sentence adds unique value.

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?

No output schema, so description should hint at return format. It says 'retrieve a value' and 'list all saved keys', but doesn't explicitly describe the returned structure (e.g., key-value pair or array of keys). Still adequate for a simple tool and includes scoping and pairing context.

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 baseline is 3. The description adds meaning beyond the schema by explaining that omitting the 'key' parameter lists all keys, and provides usage examples (ticker, address, notes). This practical context justifies a 4.

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 the tool retrieves a value saved via 'remember' or lists all keys when no key is provided. It uses specific verbs and resources (retrieve, list keys) and differentiates from siblings like 'remember' and 'forget' by naming them. Examples (ticker, address, notes) add clarity.

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 explicitly says when to use ('look up context stored earlier... without re-deriving') and how to list keys (omit key argument). It implicitly distinguishes from 'remember' (save) and 'forget' (delete), but does not explicitly state when not to use or name alternative tools beyond these siblings.

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