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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=true, so safety is covered; the description adds genuinely new billing behavior: 1 credit per successful request, native empty results still charged, scraper failures not charged, and repeated requests may re-purchase the same data. It does, however, contain a self-contradicting price line ('at least 10 Nexscope credits' versus '1 credit per request'), which muddies the cost model an agent is meant to reason about.

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 definition is padded badly: the core two-sentence description is repeated verbatim, and fragments such as 'Cosmos Post API View Content' and '1 credit per request' are pasted in as loose marketing text. The pricing caveat sits after the repeated block, so the reader has to wade through duplication to reach the useful constraint.

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-parameter read tool that already has readOnly hints and no output schema, the description covers what an agent needs: what the payload contains, the public-only restriction, and the credit behavior. The one real gap is the conflicting cost statements, which could make an agent misjudge expense.

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?

There is a single required parameter with 100% schema coverage ('Public Cosmos post URL.'), so the schema already carries the load. The description reinforces that only public posts are addressable but adds no syntax, URL-shape, or normalization guidance beyond the schema text. 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?

The opening sentence gives a specific verb and resource (get a public Cosmos post) and enumerates the payload the caller receives: media URLs, captions, source links, and save count. That is enough to separate it from siblings such as social_cosmos_search or social_cosmos_user_posts. It stops short of naming any alternative tool, so it is clear but not sibling-differentiating.

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?

The description states the key eligibility condition (public only; private or login-restricted content is unavailable), which effectively implies the caller must already hold a post URL. It never says when to choose this over social_cosmos_search for discovery or social_cosmos_user_posts for enumeration. Usage is inferable rather than prescribed.

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