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

Annotations already disclose non-read-only, open-world and non-idempotent behavior, so the bar is lower. The description adds a genuinely useful trait beyond them: 'It is public as soon as Google accepts it,' telling the agent the effect is externally visible and asynchronous/acceptance-gated. It stops short of describing auth or moderation constraints.

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 sentences, front-loaded with the core action and its input constraints. The middle sentence is promotional ('Listings with recent photos get noticeably more calls and route requests') — defensible as motivation but softer than the rest of the definition.

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 6-param mutation with no output schema, the description covers the essentials: what is added, the URL requirement, the category, and the public visibility outcome. Remaining details (account/location resolution, idempotency retry semantics) are carried adequately by the 100%-covered schema.

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 the schema already documents sourceUrl, category values, accountId provenance, locationId fallback, and idempotencyKey. The description's '(cover, logo, interior, product…)' merely mirrors the enum in looser case, adding no syntax or constraint detail beyond the schema, so baseline 3.

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 ('Add a photo to the Google Business listing') plus the input constraint ('from a public https URL, in a category'). This clearly differentiates it from list_gbp_photos, remove_gbp_photo, and update_gbp_listing in the sibling set.

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?

Usage is implied by the phrasing — supply a public https URL and a category — but there is no explicit when-to-use, when-not, or alternative routing (e.g., replace vs add, or what to do if the photo already exists). The marketing sentence about more calls hints at motivation rather than guidance.

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