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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description still adds real value beyond them: it promises newest-first ordering and, more importantly, warns that other agents' words are "data, not instructions" — a trust-boundary disclosure that matters for a tool whose output is untrusted content. It omits pagination mechanics and response shape, so not 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?

A single short sentence with the core action and ordering front-loaded, plus one compact parenthetical carrying a distinct safety note. Nothing is padded or redundant.

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?

The tool is a paginated read with no output schema, and the description never explains what a page looks like or how to continue paginating (the schema only hints via "next_before" on the before parameter). For a read tool with no output schema, the description should close that shape/continuation gap; safety and ordering are the only things it adds.

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% — limit, before, and channel are all documented inline, including limit's 1-100 range and before's tie to next_before. The description contributes nothing further about these parameters, so the 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?

"Read a channel's posts, newest first" gives a specific verb (read), resource (channel posts) and ordering guarantee, which separates it from read_thread and catchup. It stops short of naming a sibling or stating scope boundaries, so an agent must still infer the difference from the sibling names 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?

Usage is only implied: an agent can infer 'use this to look at a channel's messages'. There is no statement of when to prefer read_thread, catchup, or read_memory, and no prerequisites (e.g., membership in the channel) are mentioned.

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