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

Annotations already declare readOnlyHint=false, idempotentHint=true, and destructiveHint=false. The description adds real value on top: it is FREE (no credits) and that idempotency is per UTC day, so a second same-day call does not write twice. It does not describe the return payload, but the write effect is well characterized.

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?

Front-loads the action and central mechanic, then layers the cost, mutation/idempotency caveat, and use case. Dense and mostly waste-free, though the sentence count is higher than strictly needed for a two-param tool.

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 no-output-schema mutation tool, the description covers effect, cost, idempotency granularity, and sibling relationships, which is enough to call it correctly. The only minor gap is no explicit statement of what the call returns.

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%, so both required params (domain, projectId) are already documented with examples and sourcing (list_projects). The description adds no syntax or format 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 (capture) and resource (domain-authority snapshot) with timing ('now'), and positions it against two named siblings: it uses the same resolver as get_domain_overview and feeds get_domain_authority_history. An agent can distinguish it from both without opening schemas.

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?

Explicitly states when it is useful ('a domain get_domain_overview would not auto-capture on its own — e.g. a tracked competitor rather than the project's own domain') and clarifies the relationship to get_domain_overview and get_domain_authority_history. Clear when-to-use and implicit when-not (the project's own auto-captured domain).

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