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

With no annotations, the description carries the full burden and does meaningful work: it discloses that the link is followed safely server-side (implying a non-destructive, sandboxed read), lists the concrete detection categories, and describes the return payload ('verdict, checks, certificate and share link'). It stops short of stating auth requirements, rate limits, or behavior on unreachable URLs.

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?

Two sentences, front-loaded with the core action, then the detection detail, then the return shape. Every clause carries information; there is no filler or restatement of the name.

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 one-parameter tool with no annotations and no output schema, the description covers purpose, mechanics, and return contents, which is nearly everything an agent needs to invoke it correctly. Remaining gaps are minor: no statement about invalid input, network failure, or explicit read-only guarantee.

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% for the single 'url' parameter, which already documents that a full http:// or https:// link is required. The description adds only the 'one web link' cardinality hint, which is consistent with but not richer than the schema, so the baseline of 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 and resource ('Check one web link') and enumerates exactly what is tested: look-alike domains, domain age, sender rules, and the URLhaus known-bad list. The word 'one' implicitly separates it from the plural sibling screen_urls, but neither sibling is named as an alternative, so sibling differentiation is only suggested rather than stated.

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?

Usage is implied by the title ('Check a suspicious link') and by the description's emphasis on inspecting a single link, but it never says when to reach for check_url versus screen_urls for a batch or check_message for a different resource type. No prerequisites, exclusions, or rate-limit guidance are given.

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