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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so safety is covered. The description adds the non-obvious behavioral fact that this tool returns only a link and does not administer the test itself, which prevents misuse. It does not mention anything about link lifetime or delivery format, so it stops short of a 5.

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 short sentences, zero filler. The exclusivity constraint is front-loaded and the alternative follows immediately, in the order an agent needs them.

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-optional-parameter, read-only link generator this is nearly enough: purpose, scope and the correct alternative are all present. What is missing is the return shape (is the link returned as text, and can the agent pass 'source' meaningfully), which no output schema covers.

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?

There is a single optional parameter whose schema description is complete (utm_source naming). The description says nothing about 'source' or its default 'mcp', so it adds no meaning beyond the schema; with 100% coverage 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 resource (the web-version link of the test) and narrows it with an emphasized 'ТОЛЬКО', so an agent immediately knows this returns a link and nothing else. It also names the sibling ruforge_diagnostic_start, making it distinguishable from the in-chat diagnostic tools without opening a schema.

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?

Gives an explicit condition for use ('если пользователь хочет пройти в браузере') and an explicit alternative with its own behavior ('ruforge_diagnostic_start — он выдаёт вопросы и принимает ответы'). The routing decision is fully determined.

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