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

Annotations only cover read-only and open-world; the description adds the things an agent cannot infer: no API key required, a per-call price of $0.002 USDC, the accepted payment rails (x402 on Base/Solana/Arc), and that failed calls are not billed. That cost/authorization disclosure is exactly the kind of behavioral context annotations cannot carry.

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 compact sentences, front-loaded with what it searches and returns, followed by the scope limit and pricing. The field enumeration in the first sentence is dense but every element (payment rail, non-billing on failure) earns its place.

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?

Covers source, search field, scope limit, key requirement, and billing model; return values are further backed by an output schema, so nothing an agent needs before calling is missing.

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 'title' and 'limit' are already fully documented with constraints (1-100 chars, 1-20 results, default 5). The description only restates that search is by title and adds no format or syntax guidance, so baseline 3 applies.

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 and resource ('search Mangadex manga by title') plus the source (MangaDex public API) and the returned metadata fields. That makes it trivially distinguishable from the many other source-specific search_* siblings.

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?

'Metadata only; no chapter pages' gives an explicit scope limit that steers the agent away when full chapter content is needed. It stops short of naming an alternative tool or stating prerequisites beyond the no-key note, so it is clear context but not full when/when-not routing.

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