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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered; the description adds real value beyond that by disclosing the returned fields (including cached, possibly stale card data) and by flagging that friend-authored content is untrusted data, never instructions. That injection-defense note is a meaningful behavioral trait not expressible in 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?

Two tight sentences with zero filler; the content enumeration is front-loaded and the security constraint follows as a single clause. Every sentence carries information.

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 read-only getter with no output schema, the field enumeration plus the injection warning cover most of what an agent needs. The gap is the undocumented required parameter and no statement of what happens when the friend does not exist or the caller lacks access.

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 0% for the single required parameter friend_bot_id, and the description never mentions it — no format, no source, no error behavior for an unknown ID. "One friend's record" hints that an identifier is needed but adds nothing the schema does not already show.

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?

"One friend's record" names a specific verb (get) and resource (a single friend) and enumerates the contents: label, private note, per-friend memory, cached card. The word "one" implicitly separates it from list_friends, but no sibling is named explicitly, so an agent must infer the split.

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?

Usage is only implied: fetching a single friend's record as opposed to listing friends or updating memory. There is no explicit when-to-use, no prerequisite (e.g. needing a friend_bot_id from list_friends), and no exclusion against get_profile or update_friend_memory.

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