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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the bar is lower. The description still adds a genuinely useful behavioral fact beyond the schema: the result is a bounded range (earliest and latest only), not an enumeration, which prevents an agent from assuming it can page through all versions.

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?

A single sentence with the return scope front-loaded and the follow-up tool named at the end. Nothing is redundant and nothing needs to be re-read.

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?

Annotations cover the safety profile, an output schema covers the return shape, and the schema covers both parameters, so the description only needs the one thing structured fields cannot express — that the output is a range, not a list — and it delivers that. Minor gap: no mention of behavior for apps with zero or one version.

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 both parameters already document the 'provide this or app_id' mutual-exclusivity rule. The description's '(by slug or id)' merely restates that, adding no format, precedence, or validation detail 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 precise verb and resource: 'Get the earliest and latest version numbers of an app (by slug or id)'. This also corrects the potentially misleading name 'list_app_versions' by clarifying it returns a range, not a full list, and it distinguishes itself from the sibling get_app_version.

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 names the follow-up/alternative tool and the condition that selects it: use this 'to know the range you can fetch with get_app_version'. It stops short of stating when not to use it (e.g. if you already know the version number), but the routing intent is clear.

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