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

Annotations already declare readOnly, idempotent, non-destructive and open-world, so the safety profile is covered. The description adds genuinely non-structural context: the tool needs a user-supplied third-party API key, with a signup URL, which is the main operational gotcha. It stops short of mentioning rate limits, result caps, or pagination, so it is strong but not exhaustive.

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 dense sentences, no filler, with the credential requirement and the fallback placed last where they matter most after the agent knows what the tool does. Every clause carries information the agent needs.

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?

An output schema exists, so return values need not be explained, and the auth/alternative guidance is covered. However, for a 7-parameter tool at 14% schema coverage, the nine-of-ten undocumented parameters (timestamp cursor, language, category exclusion) leave the agent guessing at filtering behavior.

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 only 14% — solely `_apiKey` is documented — so the description must carry the rest. It adds real meaning for `categories` (naming BTC, ETH, Trading, Regulation, which is valuable since there are no enums) and `feeds`, but leaves `lTs`, `excludeCategories`, `lang`, and `sortOrder` entirely unexplained beyond a bare example.

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?

Opens with a specific noun phrase — 'CoinDesk Data (formerly CryptoCompare) aggregated crypto news feed' — then enumerates the content it returns (headlines, exchange announcements, regulatory updates, market analysis). This is a retrieval tool whose resource and scope are unmistakable, and it is distinguishable from cryptocompare_price and the news_* siblings without consulting any schema.

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 an explicit when-to-use condition (filter by category or feed) and a clear when-not plus alternative: 'Requires your own CoinDesk Data API key — for crypto news without one, use the crypto-feeds pack instead.' The agent can route correctly on the single most likely failure mode (missing credentials) without trial and error.

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