Read your X direct messages

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

Annotations declare readOnlyHint=true and openWorldHint=true, but the description goes far beyond: it discloses credit billing per message returned, the 30-day retention limit with no date filter, the lack of a conversation-list endpoint requiring event-based grouping (with the consequence that old conversations may not appear), and the reconnection requirement for pre-shipment accounts. No contradiction with annotations.

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 long but information-dense; every sentence contributes (purpose, usage examples, costs, data retention, implementation details, auth). It front-loads the core purpose and then proceeds logically through operational caveats. While slightly verbose, it avoids fluff and earns its length.

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?

Despite lacking an output schema, the description explains the return format (conversations, newest first, with message content) and covers billing, data retention, grouping behavior, and authentication requirements. For a read-only tool with no output schema, this is fully complete — nothing an agent needs to call it correctly 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?

Schema description coverage is 100%, and each parameter already has a descriptive comment (e.g., maxResults includes billing warning, paginationToken explains walking history). The tool description repeats the cost warning and default but adds no new semantic information beyond what the schema provides. Baseline 3 is appropriate.

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 and resource: 'Read the direct messages sent to the connected X account and group them into conversations, newest first'. It clearly differentiates from sibling DM tools (list_telegram_dms, list_bluesky_convos) by explicitly tying to 'X' and providing example user intents. The purpose is unambiguous.

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?

Provides concrete usage triggers ('any new DMs on X', 'what did they say') and routes replies to send_x_dm. It also warns about cost and data retention caveats. However, it does not explicitly contrast with other platform DM tools or state 'use this only for X', though the X-specific naming makes that implicit.

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