Vultr MCP

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

No annotations are provided, so the description carries the full burden. It mentions pagination via 'per_page' and return of 'Invoice line items with details', but lacks critical behavioral details: whether this is a read-only operation (implied by 'List' but not explicit), rate limits, authentication requirements, error handling, or format of returned details. For a tool with no annotation coverage, this leaves significant gaps in understanding its behavior.

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 well-structured and front-loaded with the core purpose, followed by brief parameter and return explanations. Every sentence adds value without redundancy. It's appropriately sized for a simple list tool, with no wasted words or unnecessary elaboration.

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 no annotations, 0% schema description coverage, and no output schema, the description is incomplete. It covers the basic purpose and parameters but lacks behavioral context (e.g., safety, limits), detailed parameter semantics, and output specifics (what 'details' include). For a tool with minimal structured data, this leaves the agent under-informed about critical aspects like error conditions or result format.

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 0%, so the schema provides no parameter descriptions. The description adds basic semantics: 'invoice_id: The invoice ID' and 'per_page: Number of items per page (default: 25)', clarifying purpose and default. However, it doesn't explain parameter formats (e.g., invoice ID structure), constraints, or examples, leaving some ambiguity. Since there are only 2 parameters and the description covers both, it meets the baseline but doesn't fully compensate for the lack of schema details.

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 with 'List items in a specific invoice', specifying the verb 'List' and resource 'items in a specific invoice'. It distinguishes from siblings like 'list_invoices' (which lists invoices, not items) and 'get_invoice' (which retrieves invoice details, not line items). However, it doesn't explicitly differentiate from other list tools like 'list_records' or 'list_billing_history', which is why it's not a perfect 5.

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 doesn't mention prerequisites (e.g., needing an existing invoice), exclusions, or comparisons to sibling tools like 'get_invoice' (which might return some item details) or 'list_invoices' (for broader listing). The agent must infer usage from the purpose alone.

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