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

Annotations only declare readOnlyHint/openWorldHint; the description adds real behavioral context beyond that: result ordering, the unread-until-marked persistence rule, the 1-100 limit with a 25 default, cross-workspace behavior, and the presence of a `note` field framing message content as person-authored data rather than agent instructions.

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?

Front-loaded with the core purpose, then defaults, then filters, then the safety note — a sensible ordering with no filler sentences. It runs slightly long, and the prompt-injection warning, while valuable, is dense enough to warrant a tighter phrasing.

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 covers enough of the return shape (ordering, the `note` field) and all four parameters for an agent to call it correctly. It stops short of describing the remaining message fields or pagination behavior beyond the limit cap.

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 description coverage is 0%, so the description must carry the load and it does: senderId is defined as the sender's userId, workspaceId is explained including the no-value fallback to all workspaces, includeRead is explained behaviorally, and limit gains a range (1-100) and default (25) that the raw schema does not express.

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?

States a specific verb and resource ("Lista tu bandeja de mensajes directos") plus scope — only messages other workspace people wrote to you — and ordering (most recent first). This clearly separates it from get_message (single fetch), send_message, and mark_message_read.

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?

Explicit about the default behavior (unread only) and how to widen it with includeRead=true, plus the filter semantics for senderId and workspaceId. It routes the agent to mark_message_read for the state change, though it never explicitly contrasts with get_message for retrieving a single message.

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