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. While it mentions the core mutation action (marking emails), it doesn't address important behavioral aspects like whether this requires specific permissions, what happens if emails don't exist, whether changes are reversible, or any rate limits. The description provides basic operational context but misses critical behavioral details for a mutation tool.

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 perfectly concise with two sentences that each earn their place. The first sentence states the core purpose, and the second provides essential usage guidance about account handling. There's zero wasted text, and information is front-loaded appropriately.

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 6 parameters, no annotations, and no output schema, the description provides adequate basic information about what the tool does and account handling approaches. However, it lacks important contextual details about error conditions, permissions required, what the response looks like, or how it differs from similar sibling tools like 'batch_mark_read'.

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?

With 100% schema description coverage, the baseline is 3. The description adds some value by explaining the relationship between account_id and email_accounts parameters ('Pass account_id when operating within a single account, or provide email_accounts mapping for mixed-account batches'), which helps understand when to use each approach. However, it doesn't provide significant additional parameter meaning beyond what the comprehensive schema already documents.

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 one or more emails as read or unread') and resource ('emails'), distinguishing it from siblings like 'batch_mark_read' by mentioning both read/unread operations and multi-account capabilities. It provides a complete picture of the tool's function beyond just the name.

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 different parameter approaches ('Pass account_id when operating within a single account, or provide email_accounts mapping for mixed-account batches'), giving practical guidance. However, it doesn't explicitly mention when NOT to use this tool or name specific alternatives among siblings like 'mark_email_read' or 'mark_email_unread'.

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