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

Annotations only indicate readOnly=false and destructive=false, so description carries the burden of explaining side effects. It clearly states the upload stores the signature in the partner profile and that it will be inserted into outgoing letters. It could add details about overwrite behavior or size limits, but these are not critical for basic invocation.

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 concise and front-loaded with the core action. Repeating the content in English after German adds length but serves bilingual clarity without being verbose. Every sentence contributes either the purpose, the use context, or the format constraint.

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 upload tool with no output schema, the description gives essential context about storage and usage, but it omits what the response contains (e.g., an ID or success status) and does not address potential overwrite behavior or file size limits. These gaps are noticeable but not severe given the low complexity of the tool.

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 75%, with pngBase64, widthMm, and displayName already described in the schema. The description adds the note that only PNG is supported, which reinforces the meaning of pngBase64. However, it does not elaborate on reasoning, and the schema already covers most parameter semantics, so the added value is minimal.

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 uses a specific verb and resource ('uploads a signature as PNG and stores it in the partner profile') and clarifies its role in the letter-sending flow. It clearly distinguishes itself from sibling upload tools like letterhead_upload or attachment_upload_image by specifying 'signature' and the PNG format.

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 implies when to use the tool by explaining that the signature is inserted below the letter body on sending, giving a clear context. However, it does not explicitly name alternatives or state when not to use it (e.g., for letterheads or general images). The 'Only PNG is supported' constraint partially guides format selection but not tool selection.

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