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

Annotations declare readOnlyHint: true, but the description says 'Send one transactional email' – an external side effect that contradicts read-only semantics. This is an annotation contradiction, so per rules the score is 1.

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 three concise sentences: the first states the core action, the second lists inputs and outputs, the third gives use cases. It is front-loaded and every sentence adds value, with no fluff.

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 purpose, use cases, parameters, and return values, and an output schema exists. However, it omits how the Postmark server token is provided (e.g., header), does not mention that either htmlbody or textbody is required by the API, and does not discuss rate limits or idempotency. Given the annotation contradiction, the description is not fully 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 description coverage is 0%, so the description must compensate. It lists all parameters ('from, to, subject, HTML and text bodies, cc, bcc, reply-to, custom headers, tag, open and link tracking flags, and message stream') but does not explain each parameter's format, constraints, or behavior beyond the property names already in the schema. It adds a basic mapping but lacks deeper semantics.

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 a specific action ('Send one transactional email') with a specific resource ('Postmark delivery API'), includes the endpoint, and lists parameter categories and return values. It distinguishes from sibling tools like send_batch by explicitly saying 'one transactional email'.

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 use cases ('deliver a receipt, password reset, alert, or notification message') and the context of using Postmark, but does not explicitly mention when not to use this tool or name alternative tools (e.g., send_batch). This is clear context without exclusions.

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