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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, but the description adds substantial context beyond them: encrypted messages return a marker, the server holds no key, retries will not help, metadata still comes back, and verification codes appear on their own line. These are exactly the behavioral details an agent needs to avoid misreporting encrypted content as empty.

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 purpose is front-loaded, followed by focused edge-case behavior for encryption and verification codes. The description is somewhat longer than a bare definition, but each sentence addresses a real failure mode; it avoids bloat while remaining readable.

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?

With no output schema, the description should carry more of the return-value burden. It covers critical encrypted-message and verification-code cases, but it does not describe the general shape of 'detailed information' — such as messages, participants, attachments, labels, or pagination — leaving an agent to infer the normal response structure.

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?

There is one required parameter, threadId, and the schema provides 0% description coverage for it. The description only refers to 'a specific email thread' and does not explain the parameter's format, expected identifier type, or give any example, so it does not compensate for the schema gap.

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 states a specific verb and resource: 'Get detailed information about a specific email thread.' That is clear enough for an agent to identify the operation. It does not, however, explicitly distinguish this from close siblings such as getThreadSummary, getRawMessage, or listThreads, leaving sibling differentiation to inference.

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 gives useful handling guidance for encrypted messages ('Relay such a message as encrypted. Never report it as empty.') and verification-code emails. But it never explicitly says when to choose getThread over alternatives like getThreadSummary, getRawMessage, or listThreads, so general usage is only implied by the purpose statement.

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