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

Annotations already cover the read-only/idempotent safety profile, and the description adds substantial non-obvious behavior: in-flight batches silently return status without per-page data, the call consumes rate limit but never test credits, and it quantifies context savings (~1.6 MB to a few KB for 10 URLs).

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?

Front-loaded with the payload description before the routing and prerequisite notes, and every clause carries distinct information. The sentences are long and comma-chained, which costs some readability, but nothing is padding.

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 single-parameter read tool with an existing output schema and full annotation coverage, the description covers purpose, prerequisites, cost, edge-case behavior, and sibling routing. An agent has everything needed to invoke it correctly.

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 parameter with 100% schema description coverage, so the schema already documents batchId and its provenance. The description adds no additional syntax or format detail beyond what the schema states, 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 specific verb and resource ('Compact per-page results and pre-computed aggregates for a completed visibility testing batch') and enumerates exactly what is returned. It clearly distinguishes itself from siblings gvt_get_test_results (element-level detail) and gvt_get_batch_status (polling).

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?

Names the workflows it serves (audit, status reports), the alternative it replaces (one gvt_get_test_results per URL), the prerequisite (batch must be completed, poll gvt_get_batch_status first), and the fallback for element-level detail. Explicit when-to-use and when-not-to-use.

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