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

Beyond the readOnly/openWorld annotations, the description discloses a great deal an agent could not otherwise know: the free tier is 20 calls per client per UTC day and is shared across the Spain tools, exhaustion produces an error naming a paid HTTP endpoint, that endpoint costs $0.002 USDC per successful call via x402 on Base with no account or API key, and the data comes from the BOE open data API with no official AEBOE affiliation. That is exactly the quota, failure-mode and cost context annotations do not cover.

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?

Purpose and return shape are front-loaded in the first two sentences, with quota and payment mechanics trailing. The single dense block is efficient, but the x402/Base pricing clause is long enough that structure (e.g. splitting limits from payment fallback) would aid scanning during tool selection.

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 still tells the agent what comes back (titles, issuing body, official PDF/HTML links), notes the Sunday gap that affects date defaults, and covers quota exhaustion and the paid fallback. Nothing needed to invoke or budget the call 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 coverage is 100%, so the baseline is 3, but the description earns credit by decoding section semantics the schema only lists as bare codes — 5A as tenders and 2B as public-exam calls. It also reinforces that searching is keyword- and section-scoped and tied to a specific day, though it adds nothing on q's accent-insensitive AND-matching beyond what the schema already says.

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 verb and resource ("Search the daily summary of Spain's Official State Gazette") and enumerates the content types (laws, royal decrees, orders, grants, tenders, public-exam calls) with section codes. It is clearly distinct from every sibling, none of which touch BOE, so an agent can select it without ambiguity.

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?

It establishes the usage context (keyword + section search over a single day's summary), states the caveat that there is no issue on Sundays, and explicitly flags that the 20-call daily quota is shared with es_pvpc_prices, which matters for call budgeting. It stops short of naming a when-not-to-use alternative, which is unsurprising since no sibling overlaps, so it lands just below the top.

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