ncloud_sens_upload_sms_attachment

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

Beyond the annotations (only destructiveHint=false), the description discloses several behavioral traits: constraints (≤300 KB, ≤1500x1440, 6-day retention), JSON-with-Base64 not multipart, reuse of same name/size files, and the Forbidden error meaning the service lacks the channel. The only minor gap is not stating the file ID persistence/cleanup explicitly, but 6-day retention is stated.

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 a compact 4-sentence block with all key info: endpoint, format, size limits, retention, return value, and reuse behavior. Every sentence carries operational meaning. Slight structural improvement would be separating the 'what it does' from constraints, but it's efficient.

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 there is no output schema, the description correctly identifies the returned fileId and how it's used. It also provides capacity/size constraints and error semantics. Missing details are minor, such as whether the fileId is returned in the body or as a header, but the description covers the key operational needs for an agent to call this tool correctly.

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%, so all three parameters are already documented in the schema. The description adds meaning by stating the fileBody is a Base64-encoded image with optional prefix stripping (already in schema) and that fileId is the return value. It also enriches serviceId semantics by pointing to ncloud_sens_list_projects and the channel-enabled requirement, which goes beyond the schema's NRN-form explanation.

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 uploads a JPG/JPEG image for MMS, names the exact endpoint, and specifies the return value (fileId for ncloud_sens_send_sms files[]). The verb 'upload' plus the resource and purpose distinguish it from the very large sibling list, including other SENS tools.

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 explicitly ties the output to ncloud_sens_send_sms files[], which implies the main usage flow: upload attachment then reference fileId in send SMS. It also explains the reuse behavior for same name/size. However, it doesn't explicitly contrast with alternative attachment-upload or image tools in the SENS family (e.g., ncloud_sens_list_brandmessage_images), so the when/alternative guidance is present but not fully explicit.

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