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

Annotations already indicate the tool is not read-only and not destructive. The description adds the requirement for an authenticated account and implies an external side effect (sending a message). It does not disclose details like rate limits, success/failure behavior, or irreversibility, but for a simple message-sending tool this is reasonable. The description does not contradict the annotations.

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 front-loaded with the purpose in the first sentence and is generally compact. The sentence 'Provide the listing ID and the message to send' is somewhat redundant given the schema, but the overall length is appropriate and each other sentence contributes useful context.

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 simple two-parameter action with no output schema, the description covers the core aspects: what it does, the authentication requirement, and how to obtain the listing ID. It does not explain differences from contact_broker or what happens after sending, but these are minor gaps given the tool's low complexity.

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?

The schema has no property descriptions and schema coverage is 0%, so the description must compensate. It names both parameters ('listing ID and the message') and provides the crucial semantic link that listing IDs come from search_businesses. This is more than just restating the schema, adding practical meaning to the parameters.

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's function: 'Send a contact message to a seller on Venturu by their listing ID.' It identifies both the action (sending a message) and the resource (a seller via listing ID). The use of 'seller' differentiates it from the sibling tool contact_broker, which targets brokers.

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 guidance on prerequisites ('Requires an authenticated Venturu account') and tells the user to 'Use search_businesses to find listing IDs,' which is a helpful pointer. However, it does not explicitly distinguish when to use this tool versus the sibling contact_broker, so it falls short of giving full alternatives or exclusions.

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