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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered; the description adds real value by clarifying the two mutually exclusive result modes (prepaid credit vs. monthly free quota) and that calls are non-metered. It does not cover behavior on an unauthenticated/expired account or the response shape, but for a trivial read this is solid.

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 what is returned, ending with the key constraint ('Does not consume credit'). No filler or restated title.

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 zero-required-parameter read with no output schema, the description adequately covers both possible return modes and the account scope. Minor gap: it doesn't indicate what happens when no credit or no signed-in email exists, which matters since there's no output schema.

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?

Only one optional parameter exists and the schema documents it fully ('Optional; set true if your client requires an argument. Ignored.'). The description says nothing about 'confirm', but with 100% coverage and a no-op parameter, the schema carries the burden completely.

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 concrete verb ('Show') and concrete resources (remaining intro prepaid credit in USD and encodes, or free-tier monthly encode quota), scoped to the signed-in email. It is clearly a read-only account lookup and implicitly distinct from the 'encode' sibling via 'Does not consume credit', though it never names that sibling.

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?

The line 'Does not consume credit' implies this is safe to call before encoding, and 'either/or' language implies it adapts to account type, but there is no explicit when-to-use vs. the 'encode' sibling or guidance on how often to poll it. Usage is inferable rather than stated.

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