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

Annotations already establish read-only, idempotent, non-destructive behavior, so the safety profile is covered. The description adds real value beyond that by disclosing the data scope: counts are computed 'from the latest 100 of each,' which tells the agent results may be truncated for large projects. No permission or error behavior is mentioned, but that gap is minor here.

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?

Three tight sentences with no filler, and the trigger condition is front-loaded before the return shape and the exclusion. Marginally verbose in the first sentence, but every clause carries information.

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 read-only aggregate over a single required project id, the agent knows what question this answers, what it returns, the truncation caveat, and what it is not for. With an output schema present, no further return-value documentation is needed, and nothing required to invoke it 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 description coverage is 100%, so both projectId and expectedDevices (including its default of computer/tablet/smartphone and the 1-10 name constraint) are already fully documented in the schema. The description adds no syntax or format detail beyond that, so the baseline 3 is correct.

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 (project localization summary) and enumerates exactly what it covers: video and voiceover counts per language, video counts per device, plus missing entries. It explicitly distinguishes itself from the per-tutorial siblings with 'Not for one tutorial's videos,' so an agent can separate it from get_tutorial/get_video without opening a schema.

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?

Opens with a concrete triggering condition ('Use this when someone asks which languages or devices a project still lacks...') and adds a when-not ('Not for one tutorial's videos'). It stops short of naming the alternative tool to call instead, which is the only thing keeping this from a 5.

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