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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), so the description's job is to add context and it does: default page size of 50, ceiling of 200, and the notable 'a large project can take 20 s or more to read' latency warning. It stops short of describing pagination or error behavior, but the added operational context is real.

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 dense paragraph that front-loads purpose and hits scoping, defaults, limits, latency and endpoint in order. Nothing is wasted, though the middle clauses about project scoping are slightly packed and could be broken out.

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?

With no output schema, the description still conveys the shape of results (newest first, reference id, upload flag) and the default/limit behavior. Minor omissions remain around pagination beyond the limit and ordering guarantees across projects, but an agent has enough to call 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?

Schema description coverage is 100%, so baseline is 3, but the description adds meaning the schema lacks: the concrete parameter syntax for downstream use (referenceImage_N / referenceVideo_1), which projectId to pick in practice, and what 'uploadsOnly' excludes. This is value beyond the field-level descriptions.

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 ('List the images and videos in a Google Flow project'), specifies ordering ('newest first'), and describes what each item carries (reference id, upload flag). It is clearly distinguishable from siblings like flow_list_characters, flow_list_voices and flow_upload_image.

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 tells the agent which projectId to pass and when: default main project for API generations, or the id from flow_agent_get_settings for agent-made media. It also explains the uploads-only scope and how returned reference ids feed into flow_agent_chat, so the routing decision is fully specified.

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