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

Goes well beyond the annotations: discloses that it makes a real call (two for CSRF writes), always returns 200 while the real outcome is `passed`, truncates the site response at 10,000 chars, does not echo the request, uses a 15s timeout and 1 MB cap, consumes request budget, and is limited to 30 tests/min with `429 test_rate_limited` and `Retry-After`. Annotations (destructive, non-idempotent, open-world) are consistent; the description adds substantial operational context.

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?

Dense but front-loaded: the core mechanism leads, and the remaining sentences (truncation, timeout, budget, rate limit) each carry operationally useful facts. The only waste is the leading repetition of the title, and the run-on paragraph could be structured more cleanly.

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?

Despite having no output schema, the description fully explains the return semantics (always 200, `passed` is the outcome, truncated body), plus timeout, size, budget, and rate-limit behavior. For this tool's complexity, an agent has everything needed to call and interpret it 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 tool_id, agent_id, and inputs are already documented by the schema. The description only reiterates that sample inputs are supplied 'with sample inputs' and adds no new syntax or format meaning beyond the schema, so the baseline 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+resource ('Test a custom API tool') and immediately explains the mechanism: one real call to your site with sample inputs, through the same path the AI's calls take, without the AI. This clearly distinguishes it from create_custom_api_tool, get_custom_api_tool, and list_custom_api_tool_runs.

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 clear context for when to use it: a validation step whose passing outcome 'lets the tool be switched on,' and it clarifies it runs through the real call path outside AI invocation. However, it never names an alternative sibling or states an explicit when-not-to-use (e.g., that you should not use it purely to inspect a tool).

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