display_name

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds one genuinely useful behavioral fact — the value is cached — but says nothing about staleness, refresh, or that it returns a plain string. Modest added value against an already-covered annotation set.

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?

Very short and front-loaded: the resource is named first, then the URL context, then the cached flag. The trailing 'Cached.' fragment is terse but informative; nothing is padded, though it reads as clipped rather than crafted prose.

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 zero-param read with annotations covering safety and no output schema, the description is close to sufficient, but it never says what the return value looks like (a string) or resolves the ambiguity against full_name/user_name. That overlap gap is the main missing piece.

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 tool takes zero parameters, so the schema carries no semantic load and the description cannot add parameter detail. Baseline 4 applies for a zero-param tool.

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 states the specific resource it returns: the account's display name. It is distinguishable from the similar-looking siblings full_name and user_name by naming the exact attribute. It is a noun phrase rather than a verb+resource statement, but the resource is unambiguous.

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 adds oblique context that the value feeds into URL construction for date-scoped endpoints, implying a reason to fetch it, but it never states when to call this versus full_name or user_name, nor any prerequisites. Usage is only implied.

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