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

Annotations already declare readOnlyHint=true and idempotentHint=true, so the agent knows it's safe and idempotent. The description adds the important behavioral detail that data is scoped to the user's identifier (IP, key hash, or account ID), which is beyond what annotations provide.

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 only four sentences, each serving a distinct purpose: function, use case, scoping, and pairing. It is front-loaded with the core functionality and wastes no words.

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 tool's simplicity (one optional parameter, no output schema), the description covers retrieval, listing keys, use case, scoping, and sibling relationships. It does not explicitly describe the return format, but this is inferable from the function. Overall, it is sufficiently complete.

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 description coverage is 100%, so the schema already documents the 'key' parameter. The description adds examples of what keys might be (ticker, address, notes), which provides additional context beyond the schema's definition, but the schema alone is sufficient for parameter understanding.

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 saved value or lists all keys. It distinguishes itself from siblings 'remember' and 'forget' by explicitly naming them as pairs. The examples of stored data (ticker, address, notes) add specificity.

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 to use this tool to look up stored context, avoiding re-derivation. It mentions alternatives 'remember' and 'forget' for save and delete operations, giving clear guidance on when to use this tool vs its direct counterparts.

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