get_attachment_image

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

With no annotations at all, the description carries the full load, and it does disclose real behavior: the call returns an image rendering, PDFs are paginated by a 1-based index, and all content (including text burned into the image) is untrusted data rather than instructions. It omits a few operational traits an agent might want, such as supported formats, size limits, or behavior on an out-of-range page.

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 core capability and its exclusion are front-loaded in the first two sentences, with parameter and safety notes trailing. The prompt-injection warning spans two sentences that could be tightened, but they carry genuine operational weight rather than filler.

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-annotation, zero-schema-coverage tool the security and pagination context is good, and no output schema means return values needn't be explained. However, the undefined `id` parameter is a genuine gap for correct invocation, and there is no guidance on failure modes such as an invalid page number.

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%, so the description must compensate, and it only partially does: it clarifies that filename is the original name and that page is 1-based (the schema only shows a default of 1). The required `id` parameter is never explained — whether it identifies the message, the thread, or the attachment itself is left ambiguous.

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 specific verb and resource ("View an image attachment, or one page of a PDF, as an image") and immediately scopes it with "Only for photos, posters and scans without text." That scope restriction is what separates it from the sibling get_attachment_text, so an agent can pick between the two without opening a schema.

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?

"Only for photos, posters and scans without text" is an explicit when-not rule, which is more than most definitions offer. It stops short of naming get_attachment_text as the alternative for text-bearing attachments, leaving the agent to infer the handoff.

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