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

Annotations already declare readOnlyHint=true, openWorldHint=false, and destructiveHint=false, so the safety profile is covered. The description adds that full design JSON is returned and that designs can be archived, but it does not state pagination, response size, or how 'partner' scoping works, leaving a few behavioral gaps.

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 concise sentences (DE then EN mirror) are front-loaded with the core action and add the key context that a design is referenced by name or id when sending. The bilingual duplication adds length but not obscurity; still slightly more verbose than strictly necessary.

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?

With annotations covering safety, no output schema needed, and only two params (one documented in schema), the description provides enough context for an agent to call the tool: it describes the returned payload (full design JSON) and the business role of the resource. Missing only explicit guidance on the reasoning parameter and archived exclusion default, which is partially in schema.

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 50%; includeArchived is fully documented in the schema, but the 'reasoning' parameter is undocumented anywhere. The description does not compensate by explaining includeArchived semantics beyond what the schema says, nor does it explain what 'reasoning' should contain. Baseline 3 for partial coverage.

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?

States a clear verb (lists), resource (letterheads/Briefdesigns), and scope (partner's saved designs with full JSON), and distinguishes it from siblings like letter_design_list_presets and letterhead_list by naming the concrete artifact a design is. The bilingual DE/EN phrasing is specific and 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?

The description explains what a design is used for (referenced by name or id when sending; carries every kind of mail), which implies the tool's context but does not explicitly say when to use this versus letter_design_list_presets, letterhead_list, or letter_design_preview. Usage is left to inference from the resource definitions.

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