photos create picker session

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

Annotations already declare readOnlyHint/openWorldHint/idempotentHint and non-destructive behavior, but the description adds the non-obvious part: this starts an interactive, external-facing session whose completion the agent must poll for. It omits session expiry and whether repeated calls spawn duplicate sessions, which are the remaining behavioral unknowns.

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?

Two short sentences, front-loaded with the action and immediately followed by the required next step. No filler or restatement of the name.

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?

Output schema covers return values and the description covers the human-in-the-loop flow, so an agent can drive the tool end to end. The only gap is the unspecified max_item_count and any session lifetime constraint.

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 0% and the single parameter max_item_count is never mentioned in the description, so nothing explains what the limit means or what happens if it is omitted. With no parameters the baseline would be 4, but here the one undocumented parameter is left entirely to inference.

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 ('Start a Google Photos Picker session') plus the outcome ('so the user can choose existing photos'). It also names the paired sibling photos_get_picker_session, so an agent can place this tool in a workflow without ambiguity.

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?

Gives a clear operational sequence: hand picker_uri to the user, then poll photos_get_picker_session until media_items_set is true. It stops short of saying when a picker is preferable to the album/media-listing siblings, so it is clear context rather than full when/when-not guidance.

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