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

With no annotations provided, the description carries full responsibility. It goes beyond the schema by explaining the side effect on send_email (SMTP sending and IMAP-APPEND to Sent folder) and discloses AES-256-GCM encryption at rest with EMAILMCP_SECRET. This is detailed 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?

Two sentences, front-loaded with the action and resource, and every clause adds value (purpose, services, effect, encryption). No redundancy or 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 the core behavior and security, and the schema fully documents all parameters. It lacks explicit mention of prerequisites like account creation (though schema says 'must already exist') and behavior on overwrite, but given no output schema, return values are not needed. Overall adequate for a 10-param tool.

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 baseline is 3. The description adds context like service examples and the encryption aspect, but individual parameter descriptions in the schema already provide examples and defaults. The description does not add substantial new meaning for specific parameters beyond what the schema includes.

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 attaches SMTP + IMAP credentials to an existing account, with a specific verb 'attach' and resource 'credentials to an existing account'. It distinguishes from siblings like create_email_account by emphasizing the existing account and personal services (iCloud, Gmail, Fastmail, Office365).

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 implies when to use it: for personal accounts with existing credentials, and notes the effect on send_email. It does not explicitly exclude alternatives or name sibling tools, but the context 'to an existing account' clarifies that the account must already exist, which is sufficient guidance.

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