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

Annotations already indicate idempotent and non-destructive behavior. The description adds the behavioral constraint about status, which is not in annotations. It could be improved by mentioning error conditions or prerequisites beyond status, but it adds value.

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?

Two concise sentences with no wasted words. The first sentence states the action, the second adds a critical constraint. Front-loaded and 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?

The description covers the core functionality and constraint, but lacks information about return values (no output schema), required permissions, or error scenarios. Given the tool's moderate complexity and absence of output schema, the description is adequate but could be more complete.

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 coverage is 100% with descriptions for all parameters. The description only explicitly mentions 'message content, media, or send time', which maps to three of six parameters (message, mediaUrl, sendAt). It does not add meaning beyond the schema, so baseline 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 verb 'Update' and the resource 'scheduled message', specifying the updatable fields (content, media, send time). It distinguishes from siblings like 'neuron_cancel_scheduled_message' by adding the constraint that only messages with status 'scheduled' can be updated.

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 a clear condition for use ('Only messages with status scheduled can be updated'), implying when to use. However, it does not explicitly mention alternatives like cancel or create new, or when not to use it.

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