Read a message

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

Annotations already declare readOnlyHint=true, so the agent knows this is a safe read operation. The description adds scope ('full headers and body text') but does not disclose any additional behavioral traits such as error handling, rate limits, or message-not-found behavior. It adds some value beyond annotations but not rich context, consistent with a mid-range score.

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 a single sentence of 12 words, front-loaded with the verb and resource. Every word contributes meaning, including 'full', 'headers', 'body text', 'by uid', and 'within a folder'. There is no filler or redundancy.

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?

No output schema exists, so the description's mention of 'headers and body text' communicates return content. It also clarifies the folder parameter. Given the tool's low complexity and strong readOnly annotation, the description is nearly complete, though it omits edge-case behavior (e.g., missing uid) and the uidvalidity safety mechanism is only in the schema.

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 67% (uid has no description, folder has default, uidvalidity has description). The description adds 'by uid within a folder', which provides basic meaning to uid and folder, but it does not explain uidvalidity or offer syntax details. Since the schema already covers folder and uidvalidity, the description adds marginal value beyond the 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 states a specific verb ('Read'), a specific resource ('message'), and explicit scope ('full headers and body text') with identifiers ('by uid within a folder'). This clearly distinguishes it from sibling tools like get_headers, which likely reads headers only, or search_mail, which finds messages.

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: use this when you have a uid and want a single message's full content. It implies that get_headers would be for headers alone, but it does not explicitly name alternatives or state when not to use this tool. No exclusions are mentioned, so it earns a 4 rather than a 5.

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