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

Annotations already establish readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description adds genuine context beyond that — 'No fetch or generated consensus' (it will not synthesize), 'bounded', and 'No key, credits, wallet or preparation needed' — but says little about the 'Existing source and input limits' it vaguely references.

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 core purpose is front-loaded, but the text is fragmented into choppy sentences and padded with promotional framing ('FREE during validation') and the redundant 'Supply your task in input', which do little to help invocation.

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?

An output schema exists, so return values need no explanation, and the description covers the general data contract. However, the non-obvious input structure — a required nested object whose thread must contain exactly two items — is left entirely to the schema with no explanatory help, which is the main completeness 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 description coverage is 0%, so the description carries the burden, yet it only vaguely refers to 'bounded' (hinting at maxChars/maxComments) and 'input'. It never explains sourceUrl, the thread array's exact-two-item constraint, maxComments default of 30, or the 12000-char ceiling, leaving significant constraints undocumented.

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 (Format) and resource (supplied Reddit comments JSON) with the exact output (a bounded post and reply tree with Markdown, authors, and direct links). The clause 'No fetch' differentiates it from sibling fetch tools like web_readable_fetch and web_page_pack without needing the 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?

'No fetch' implies the caller must supply the data rather than retrieve it, which is useful context. However, there is no explicit when-to-use vs alternatives routing, and 'Supply your task in input' does not clarify the conditions or prerequisites for choosing this tool over a preview or fetch sibling.

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