Twilio SMS MCP Server

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

Annotations cover key behavioral traits: read-only, non-destructive, idempotent, and open-world. The description adds value by mentioning the tool's utility for 'cost monitoring and analytics,' which provides practical context beyond the annotations. However, it doesn't disclose additional details like rate limits, authentication needs, or specific data formats, leaving some behavioral aspects uncovered.

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 and front-loaded: a single sentence that directly states the tool's purpose and utility. Every word earns its place, with no redundancy or unnecessary elaboration, making it efficient and easy to parse for an AI agent.

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 tool's moderate complexity, rich annotations (read-only, idempotent, etc.), and the presence of an output schema, the description is reasonably complete. It covers the core purpose and usage context. However, it could be more comprehensive by mentioning sibling tools or specific limitations, but the annotations and schema provide sufficient support for basic understanding.

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 input schema has 100% description coverage for its parameters ('category' and 'days'), with clear defaults and constraints. The description doesn't add any parameter-specific information beyond what the schema provides, such as explaining 'category' options in more detail. Since schema coverage is high, the baseline score of 3 is appropriate, as the description doesn't compensate but also doesn't detract.

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 purpose: 'Retrieve daily SMS/MMS usage statistics for the account.' It specifies the resource (SMS/MMS usage statistics) and the action (retrieve). However, it doesn't explicitly differentiate from siblings like 'sms_account_info' which might also provide account-level data, though the focus on 'usage statistics' suggests a distinction.

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 clear context for usage: 'useful for cost monitoring and analytics.' This implies when to use the tool—for monitoring expenses and analyzing usage patterns. It doesn't specify when not to use it or name alternatives, but the context is helpful for guiding selection among siblings focused on messaging operations.

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