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

Annotations already declare readOnly, idempotent, non-destructive and open-world, so safety is covered. The description adds real value beyond that: each number carries its source, read timestamp, and rounding flag, and private metrics appear in not_public with a reason, plus the no-authentication constraint. It says nothing about error behavior for malformed or non-existent URLs or about rate limits, which is the main remaining gap.

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?

Purpose and metric list are front-loaded, and the closing sentence on no sign-in is a well-placed caveat. The URL-format enumeration is duplicated almost word-for-word from the schema description, which is wasted text in an otherwise tight paragraph.

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-URL read tool with a full output schema, this covers everything an agent needs: accepted inputs, what each returned number means (source, read time, rounding), how non-public metrics are surfaced, and the fundamental scope limit of no authentication. Return-value explanation is a bonus rather than a substitute for the output schema.

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?

With one parameter at 100% schema coverage, the schema already documents the accepted URL forms and the example. The description restates the same URL formats verbatim rather than adding new semantics (e.g., whether bare IDs are preferred or how short-link redirects are resolved), so a baseline 3 is appropriate.

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 ('Read the public numbers of one post') and enumerates exactly which metrics come back (views, likes, comments, shares, saves, post time). The 'one post' framing plus the platform list makes it clearly distinct from siblings like compare_posts (multiple posts) and list_channel_stats (channel level).

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 clear applicability boundaries: works on public YouTube/Short and TikTok URLs, and explicitly excludes private posts and account analytics because the tool never signs in. It does not name sibling tools or say when to prefer compare_posts or list_channel_stats, so it stops short of full alternative routing.

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