Read a message attachment (image/audio/file)

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

With no annotations provided, the description carries the full burden and does well: it discloses that attachments are decrypted, images are returned inline, and all attachments are saved to a local file with the path returned. This goes beyond the basic 'read' action, explaining side effects and output format. It does not mention potential errors or permission requirements, but the disclosed behavior is adequate for most use cases.

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 well-structured, leading with the primary purpose, then the usage pattern, then the output behavior and suggestions. Each sentence adds substantive value without redundancy or excessive length. It is front-loaded and easy to parse.

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?

Given the tool's complexity (3 params, no output schema, no annotations), the description covers all necessary operational details: how to identify an attachment, what happens with images (inline) and other types (saved locally with path), and how to leverage the content. It does not mention error conditions or format limitations, but these are not critical for an agent to invoke the tool correctly. Overall, it provides sufficient context for successful use.

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 100%, with all three parameters clearly documented (message_id required, oase_id defaults to last joined, media_index is the <n> in the attachment list and defaults to 0). The description adds no new parameter-level meaning; it merely reiterates the attachment index concept in prose. Since the schema already handles parameter semantics, a baseline of 3 is appropriate.

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 clearly states the tool downloads and decrypts attachments from chat messages, listing specific types (images, voice messages, videos, documents). It explains the mechanism for identifying which attachment via message id and index, distinguishing it from sibling tools like read_messages which focus on message content rather than attachments.

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 provides explicit guidance on how to use the tool: it explains that attachments are listed as [attachment <n>: <type> "name"] and instructs to pass the message id and index. It also offers post-processing guidance (transcribe audio, open documents) and mentions using content in responses, giving clear context. It does not explicitly state when not to use it or name alternatives, but no direct alternative exists among siblings.

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