MCP Email Service

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. While it indicates this is a mutation operation ('mark as unread'), it doesn't describe what happens on success/failure, whether it requires specific permissions, or if there are rate limits. The description adds minimal behavioral context beyond the obvious action.

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 a single, efficient sentence that front-loads the core action and includes a useful parameter note. There is zero waste, and every word earns its place in clarifying the tool's use.

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 is adequate but has clear gaps. It covers the basic action and a parameter recommendation, but lacks details on behavioral traits, error handling, or return values. Given the complexity and missing structured data, it's minimally viable but incomplete.

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 parameters thoroughly. The description adds marginal value by emphasizing that 'account_id' is optional but recommended, but doesn't provide additional semantic context beyond what's in the schema. This meets the baseline for high schema coverage.

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 verb ('mark as unread') and resource ('a single email'), making the purpose unambiguous. However, it doesn't explicitly differentiate from sibling tools like 'mark_email_read' or 'mark_emails' (batch operation), leaving some room for improvement.

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 implied usage guidance by mentioning that 'account_id' is optional but recommended, which helps with parameter selection. However, it doesn't explicitly state when to use this tool versus alternatives like 'batch_mark_read' or 'mark_emails', nor does it mention prerequisites or exclusions.

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