MCP Email Service

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 mentions the optional account_id recommendation but doesn't describe what 'mark as read' actually does (e.g., whether it updates email status permanently, requires specific permissions, or has side effects). For a mutation tool with zero annotation coverage, this is a significant gap in behavioral transparency.

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 purpose and includes only essential guidance about the account_id parameter. Every word earns its place with zero wasted content, making it optimally concise.

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 minimally complete. It covers the basic purpose and provides some parameter guidance, but lacks details about behavioral consequences, error conditions, or what happens after marking an email as read. Given the complexity of email state changes, 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 minimal value by emphasizing the account_id recommendation, 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 specific action ('mark as read'), the resource ('a single email'), and distinguishes it from sibling tools like 'batch_mark_read' and 'mark_emails' by emphasizing 'single email'. It uses a precise verb+resource combination that leaves no ambiguity about what the tool does.

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 when to use this tool by mentioning 'account_id optional but recommended to avoid cross-account lookup', which helps guide parameter usage. However, it doesn't explicitly state when to choose this tool over alternatives like 'batch_mark_read' or 'mark_emails', missing explicit sibling differentiation.

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