Unosend MCP Server

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

With no annotations provided, the description carries full burden for behavioral disclosure. It effectively reveals a critical behavioral trait: 'Charges from wallet at $0.0075 per segment' - indicating a financial transaction with specific pricing. However, it doesn't cover other important aspects like authentication requirements, rate limits, error conditions, or what happens on success/failure.

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 perfectly concise - two sentences that each earn their place. The first states the core purpose, the second adds crucial behavioral context (charging). No wasted words, well-structured with the most important information first.

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 mutation tool with no annotations and no output schema, the description does an adequate but incomplete job. It covers the core action and a critical side effect (charging), but lacks information about return values, error handling, authentication needs, or system constraints. Given the complexity of a paid SMS sending operation, more context would be helpful.

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 the schema already documents all three parameters thoroughly. The description adds marginal value by mentioning '160 chars = 1 segment' in relation to the body parameter, but this is essentially repeating schema information. No additional parameter semantics beyond what the schema provides are included.

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 ('Send an SMS message') and resource ('SMS message'), making the purpose immediately understandable. It doesn't explicitly differentiate from sibling tools like 'send_email' or 'get_sms', but the specificity of 'SMS' provides inherent distinction. The mention of charging adds context but doesn't fully articulate unique scope compared to alternatives.

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 like 'send_email' or 'get_sms'. It mentions charging implications, which could inform usage decisions, but lacks explicit when/when-not instructions or named alternatives. The agent must infer usage context from the tool name alone.

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