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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds real context beyond them: the side effect of attaching a duplicate card in chat, the rendering behavior in MCP Apps hosts, and the explicit guarantee that it never publishes, schedules, or enables a public link. That is exactly the information an agent needs to avoid a wrong call.

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 trigger condition and heavily information-dense, with no filler sentences. A few clauses are packed tightly (render behavior plus the negative publish guarantee in one sentence), but every sentence carries decision-relevant content.

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?

For a single required parameter with an output schema, everything an agent needs is present: when to call, when not to, how to get the id, and what it will never do. Return values are covered by the output schema, so their absence from the description is not a gap.

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 100% and the postId description already names its provenance (search_posts/search_post_drafts/create_post_draft). The description largely repeats that provenance, adding no format or validation guidance beyond the schema, so baseline 3 applies.

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 the specific action (open an existing post card in chat) and the resource (an existing post identified by postId). It explicitly separates itself from preview_post ('a browser preview link is different') and from create_post_draft, so an agent can disambiguate it without opening sibling schemas.

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?

Gives both triggers (author asks to open a card, requests another card, reports a missing card) and an explicit exclusion (do not call automatically after create_post_draft because it already attaches a card). It also tells the agent how to obtain the required id via search_posts/search_post_drafts.

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