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

Annotations already cover the read-only, idempotent, non-destructive, closed-world profile, and the description adds substantial behavioral detail beyond them: truncation limits, readTextTruncated/readTextLinesLeftOut, appUrl, changeKind semantics, and specific not_found cases. This is exactly the kind of context an agent needs to interpret results and handle errors correctly.

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, but the description is a single dense run-on paragraph with semicolon-separated return-field explanations. Most details are relevant given the absence of an output schema, but the structure is hard to scan and could be more 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?

With no output schema, the description carries the full burden of explaining return values, and it does so thoroughly: fieldChanges, readText, changeKind variants, word/body/html change flags, sourceLines, summary, deletedImages, appUrl, and error behavior. An agent has enough information to invoke and interpret the tool correctly.

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 coverage is 100%, so the baseline is 3, but the description adds meaningful directionality: 'from 6 to 3 is the older text against the newer' and 'to defaults to the current version.' That interpretation goes beyond the parameter descriptions, though templateId is only referenced via its source list and not further clarified.

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 opens with a specific verb and resource: 'What changed between two versions of an email template.' It immediately explains the directional comparison semantics, so an agent can distinguish this from siblings like list_email_template_versions or get_email_template.

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 context for use is clear: compare a `from` version against a `to` version, with `to` defaulting to the current version. It also documents not_found behavior for missing templates/versions. It stops short of explicitly naming alternatives such as list_email_template_versions for discovering version numbers, so it is not a full when/when-not/alternatives statement.

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