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

Annotations already declare readOnlyHint/destructiveHint, but the description adds genuinely non-structured behavior: counts are live, the call is free (no quota cost), resets_at is UTC, and unverified email sign-ups get limit_reason/verify_at. It stops short of describing rate limits or caching, but the added context is substantive.

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?

Single dense paragraph that front-loads what is read and what is returned before moving to usage guidance. Every sentence carries information, though the return-field enumeration is long and could be tightened.

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?

No output schema exists, so the description carries the return-value burden and does so fully, listing every field, its meaning (screenshots_remaining includes extra_credits), and the UTC convention. Nothing needed to call this tool correctly is missing.

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% and already documents the YYYY-MM format and current-month default, so baseline is 3; the description adds the semantic purpose ('pass month to read an earlier month'), telling the agent why it would override the default.

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 ('Read how many captures the account has used and has left') and enumerates the returned fields (plan, screenshots_used, screenshots_limit, screenshots_remaining, period, resets_at), distinguishing it from every sibling, none of which read account-level quota.

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 explicit when-to-use conditions ('before a large batch_screenshots job, or when a capture says the month is used up') and names the sibling tool it pairs with, plus the month parameter's use case for historical reads.

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