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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds genuinely useful non-annotation context: the status vocabulary (running, finished, error) and the provenance requirement that app_id must come from the project's Twinr section (replit.md, else AGENTS.md). It stops short of describing pagination or what 'newest' means when a build is in progress.

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?

The capability is front-loaded in the first sentence and the fallback workflow follows in logical order. The closing clause 'and never infer it from the project's name or URL' partially restates the preceding 'Never choose one yourself', which is mild redundancy in service of a safety rule.

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?

An output schema exists, so return values need no explanation, yet the description still names the key fields. For a one-parameter read tool the critical missing-input path is fully handled. It leaves a small gap by instructing the agent to 'record it in the project's Twinr section' without describing how that write happens or which tool performs it.

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 the single parameter carries its own description, so the schema already does the heavy lifting; baseline is 3. The description does reinforce provenance by tying app_id to the project's Twinr section and by prescribing record-keeping after resolution, but it adds no format or validation detail beyond the schema.

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?

The description names a specific verb and resource ('Get the newest Android and iOS builds of one Twinr app') and enumerates the returned fields (build number, version, status). It does not differentiate from near-neighbors like get_app or get_download_links, so an agent must inspect the schema to be certain which tool to pick, which keeps it below a 5.

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?

It gives an explicit conditional workflow for the missing-app_id case: call list_apps, show every organization and app to the merchant, and ask which app this project is. It also states a clear prohibition ('Never choose one yourself, and never infer it from the project's name or URL'). The only gap is that it does not say when to prefer this over get_app or get_download_links.

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