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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds real behavioral substance: the exact counting models per platform (X weighted 280 with emoji 2 and links 23, TikTok UTF-16 2,200, YouTube 100-char title and 5,000-byte description, hashtag and mention caps) and that it returns counts, limits and a fit verdict.

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?

Two sentences, front-loaded with the core action and return value. The parenthetical rule details are dense but each earns its place by explaining platform-specific counting; a slightly more scannable structure would help.

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?

With no output schema, the description carries the burden of explaining the return value, and it does so ('counts, limits and whether it fits'). For a read-only three-parameter tool this is nearly complete, though it never mentions xPremium's effect on the X limit, which the schema covers instead.

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%, so the schema already documents text, title and xPremium, including the 25,000-character Premium fallback that the description omits. The description's counting rules add context but do not map additional meaning onto specific parameters.

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?

The description opens with a specific verb and resource ('Counts a post's text') and names the platforms and limits it targets. It is clearly distinguishable from siblings like get_platform_specs because it evaluates a given text rather than listing specs.

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 this is for pre-post validation, but the description never states when to use it versus get_platform_specs or check_video, and offers no exclusions or prerequisites.

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