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

The description goes beyond the annotations by revealing that reading does not imply marking, that results are verified by reading back flags, that UIDs are folder-scoped requiring mailbox when not from INBOX, that batch operations can partially succeed, and that already-read messages are not errors. This level of behavioral detail is exceptional and fully sets expectations for the side effects and edge cases.

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 informative but somewhat verbose and repetitive. For example, the UID folder-scoping warning is stated twice with slightly different wording, and the emphasis on batch calling is repeated in the uids parameter description. While the content is valuable, the text could be tightened without losing meaning. It is still well-structured with clear, separated points.

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 all necessary context: purpose, usage, batching, folder semantics, verification behavior, idempotency, and relationship to undo. It even mentions partial success, which is rare in tool descriptions. Given the absence of an output schema, the note that flags are read back provides sufficient expectation of what to observe. Nothing essential for correct invocation is missing.

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?

The schema covers 100% of parameters with precise descriptions. The uids parameter explains its source (list_emails or search_emails), its batch nature (all in one call), limits (up to 500), and single-message usage (one-element array). The mailbox parameter clarifies its purpose (folder name) and default (INBOX). This leaves no room for misinterpretation.

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's purpose: 'Mark messages as read.' It explicitly distinguishes this action from merely reading a message (which does not mark it read) and from the sibling tool mark_unread, making its function unambiguous even among many related email tools.

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 explicit guidance on when to use it (when the user asks to mark as read, not during reading) and how to use it correctly: pass all messages in one call, handle UID folder-specificity by providing mailbox, and expect verification of results. It also notes idempotency and names the undo operation (mark_unread), leaving no ambiguity about invocation context.

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