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

Annotations already declare readOnlyHint=true and non-destructive, and the description adds meaningful behavior beyond them: it never accepts or reads documents, returns a fit/no-fit verdict with plain reasons, and explicitly offloads uploads, payment and power of attorney to the website. An agent knows both the safety profile and the boundary of the tool's authority.

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 trigger is front-loaded, followed by inputs, return value, and exclusions in a logical order with no filler. The site-redirect sentence is slightly tangential but earns its place by preventing the agent from attempting payment or upload actions.

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?

There is no output schema, and the description compensates by describing the return shape ('fits or does not fit with plain reasons'). Combined with the stated exclusions and full schema coverage, an agent has everything needed to call this correctly.

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 restates the three required inputs in user-facing terms ('package complete and ready', 'working Spanish digital certificate or Cl@ve', 'which procedure'), clarifying why each answer matters rather than just repeating the field names. The optional language parameter is left to the schema, which is acceptable at full coverage.

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 description names a specific verb and resource ('check whether Spain Visa Submit suits their situation') and enumerates the three required answers, so an agent knows exactly what the tool evaluates. It does not name any sibling tool directly, so differentiation comes from exclusion rather than explicit routing.

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 gives an explicit trigger ('Use when the user wants to know whether Spain Visa Submit suits their situation') plus clear when-not boundaries: no document advice, no eligibility or visa strategy, no document reading, and uploads/payment/POA belong on spainvisasubmit.com. It stops short of pointing to a specific sibling for the adjacent tasks it declines.

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