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

With no annotations provided, the description carries the full behavioral burden and does substantial work: it discloses pricing (€0.01 per page / 3000 chars), the auth requirement (Bearer API key), the return payload ('redacted text and entity positions'), and supported languages. It stops short of noting limits such as max file size, what happens when neither text nor url is supplied, or error/failure behavior.

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?

One dense, front-loaded block: what it redacts, what it returns, what it costs, then parameters — a sensible ordering for an agent. It is slightly run-on with the em-dash asides ('— via NER (en, ru, uk, de) —', 'mask → [EMAIL] (default)') but nearly every clause carries real information.

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?

For a 7-parameter, zero-annotation tool the description is close to self-sufficient: purpose, cost, auth, defaults, enum values and return shape are all present, and the existing output schema relieves it of further return-value detail. The gap is that zero parameters are required yet no statement says whether text, url, or both must be supplied.

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 0% and the description compensates for nearly all of it, explaining all seven parameters including entity names, the two mode outputs with their exact token formats ('[EMAIL]' vs '[PERSON_1]'), language options and country as the default phone region. Minor deduction because 'return_values: bool' conflicts with the schema's string type, and text/url mutual exclusivity is only hinted at.

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 opens with a specific verb ('Mask') and enumerates exactly which entity classes it handles (emails, phones, IBANs, cards, IPs, plus NER-derived names/orgs/locations), immediately distinguishing it from siblings like entity_extract or profanity_filter. Scope (text or PDF, four languages) is stated up front.

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 clarifies the in-tool input choice ('url: pdf url (alternative)' vs text) and gives defaults for entities, mode, language and country, which helps invocation. However it never names a sibling alternative (e.g. entity_extract for extraction-only, profanity_filter for simpler masking) or states when not to use it, leaving sibling routing to inference.

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