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

Beyond the readOnly/openWorld annotations, the description discloses that the underlying API is public with no key required, that results are unvetted ('quality is not checked'), and the full cost model with payment rails (x402, Base/Solana/Arc) and the fact that failed calls are not charged. That is exactly the economic and quality context an agent cannot get from structured fields.

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 dense sentences, front-loaded with the purpose followed by return fields, quality caveat, then pricing. Every sentence carries information, though the return-field enumeration is somewhat redundant with the output schema.

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?

Given only two optional params, full schema coverage, an output schema, and readOnly annotations, the description covers the remaining unknowns: data provenance, unvetted quality, authentication model, and cost. Nothing needed to call it correctly 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 both parameters (q, limit) are already fully documented in the schema. The description adds no search-syntax hints or semantics for q/limit beyond what the schema states, 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?

States a specific verb (npm registry search), a specific resource (MCP servers that convert Markdown to PDF), and enumerates exactly which fields come back (name, version, publisher, downloads, link). An agent can distinguish this from generic web/news search siblings immediately.

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 scope ('MCP servers that convert Markdown to PDF', public npm search API) implies when the tool applies, but there is no explicit when-to-use/when-not guidance and no reference to near-neighbor siblings such as search_cran_r_packages or the general web search tools. Usage must be inferred from the domain wording.

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