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

While annotations already declare the tool as readOnly, idempotent, and non-destructive, the description adds important behavioral context: it is 'Scoped to your identifier (anonymous IP, BYO key hash, or account ID)' and supports listing all keys when the key argument is omitted. This goes beyond the structured annotations and helps the agent understand scope and invocation variants.

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 sentences, front-loaded with the primary action, and every sentence contributes meaning. There is no redundant information; the pairing with remember/forget and the scoping detail are compactly included without clutter.

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 low complexity (one optional parameter), complete schema coverage, and strong annotations, the description provides all necessary context: what it does, when to use it, how parameters behave, and how it relates to siblings. Nothing important is missing.

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 provides 100% coverage for the optional 'key' parameter, but the description adds semantic value by explaining that omitting the key lists all saved keys and providing examples of what keys might represent (target ticker, address, research notes). This helps the agent understand the parameter's purpose and behavior beyond the schema's basic type description.

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's function: 'Retrieve a value previously saved via remember, or list all saved keys (omit the key argument)'. This specifies a concrete verb and resource, and it distinguishes itself from sibling tools like remember and forget by explicitly referencing them.

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 gives explicit usage context: '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.' This explains when to use the tool and contrasts with the alternative of re-deriving information. It also mentions pairing with remember and forget, clarifying the tool's role within the family.

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