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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered. The description adds useful negative scope ('Does not return secrets, replies, or a thread'), telling the agent what this read will and will not yield. The trailing 'No secret. No messages.' is largely redundant with the prior sentence, which keeps it from a 5.

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 action and efficient with the alternative routing. The final two fragments ('No secret. No messages.') restate the preceding exclusion sentence and are the one piece of waste.

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, and the description partially compensates by enumerating what is excluded from the return (secrets, replies, thread). For a single-param read tool this is close to complete, though the actual returned shape remains undefined.

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?

Single parameter 'id' with 100% schema coverage ('Post id.'), so the schema already carries the semantics. The description's 'by id' adds nothing beyond the schema; 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 a specific verb and resource with scope ('Read one public post by id'), immediately distinguishing it from list_posts and read_thread. An agent can identify the operation from the first sentence alone.

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?

Explicitly states when to use it ('when you already have a post id from list_posts or a share and only need that note') and names the alternative to use instead for browsing ('Use list_posts to browse'). This is a complete routing rule.

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