Push Flex Message

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

The annotations include destructiveHint: true, which already signals that this operation has side effects. The description adds no extra behavioral context beyond the obvious fact that it sends a message. It does not mention any rate limits, authentication requirements, or other operational details, but the annotation covers the safety profile, so this is acceptable.

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, using only two sentences to convey the core purpose and the two layout variants. It is front-loaded with the main action and target, and every word earns its place. There is no redundant or filler text.

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 extreme complexity of the message schema (nested objects, many options), the description is far too brief. It does not mention the required fields (altText, contents), the structure of the message, or any constraints. With no output schema and only 50% parameter coverage, an agent would struggle to construct a valid call without additional documentation.

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 only 50%, meaning the description must compensate for the missing parameter documentation. The description does not explain the message structure, the required fields, or the meaning of the parameters. The schema itself provides some descriptions (e.g., userId) but the message parameter is complex and undocumented. The description adds no value beyond what the schema already provides.

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 action (push) and the resource (flex message) and specifies the delivery target (to a user via LINE). It also mentions the two layout options (bubble and carousel), which adds specificity. However, it does not explicitly distinguish from sibling tools like broadcast_flex_message or push_text_message, though the singular 'user' implies a direct push rather than a broadcast.

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 no guidance on when to use this tool versus alternatives. It does not mention that this is for a single user vs. broadcast, nor does it reference the sibling tools or any selection criteria. An agent would have to infer usage from the name and context.

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