fetch_part

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

With no annotations provided, the description fully discloses behavior: how decode affects text vs binary parts, default behavior (decode=True returns decoded string), and fallback to base64 for binary or decode=False. It also explains the return format, making the tool's behavior predictable.

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 well-structured with a concise introductory sentence followed by a clear explanation of part numbers and return behavior, then a bullet-like Args list. It's informative without being verbose, though the Args section could be slightly more compact.

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?

Given the tool's complexity (4 parameters, no output schema), the description covers all necessary aspects: input parameters, behavior for different cases, return value structure, and dependency on inspect_email. It is self-contained and complete for an agent to use 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 0%, so the description must explain parameters. It does so comprehensively with an Args section detailing folder, email_id, part_number, and decode, including default values and data type implications (str vs base64). This adds significant meaning beyond the bare schema.

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 fetches a specific MIME part of an email by part number, using a specific verb ('Fetch') and resource ('MIME part'). It references inspect_email for context, distinguishing it from sibling tools that deal with bulk operations or other email actions.

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 explains that part numbers come from inspect_email's parts list, providing clear usage context. While it doesn't explicitly say when not to use it, the context is sufficient for an agent to decide. It could have mentioned alternatives for full email access, but it's adequate.

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