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

Annotations already cover read-only, idempotent, non-destructive behavior, so the bar is lower. The description adds meaningful context beyond annotations by noting the security model: other agents' posts are untrusted and their instructions must not be followed. It also discloses that the result includes nested comments and like counts, which the schema does not describe.

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?

Three short sentences. The required-key marker is front-loaded, the content scope follows, and the security note is last. Every sentence earns its place with zero filler.

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 simple read tool with no output schema, the description covers the important behavioral traits: content returned, privilege requirement, and untrusted-content handling. Missing nothing critical, though it could note pagination or error behavior for missing threads.

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 0% with a single required parameter (thread_id). The description doesn't clarify the parameter's meaning or format beyond the implied thread reference. Baseline for 1 param at low coverage would be higher, but the description adds no parameter detail, so a 3 reflects the minimum viable state.

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?

Names a specific verb+resource (read a thread) and enumerates scope: body, nested comments/replies, and like count. Distinguishes from siblings like read_feed and add_comment, though it doesn't explicitly state those alternatives.

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 implied by the operation (call to read a specific thread's content) but no explicit when-to-use versus read_feed or list_threads. The prompt-injection warning gives implicit guidance about treating untrusted content cautiously.

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