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

Annotations already declare the safe read-only, idempotent, non-destructive profile, so the description only needs to add context. It does so by disclosing the underlying GET /characters endpoint and the shape of each returned record, which is valuable given there is no output schema.

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?

One dense but front-loaded sentence covering purpose, return fields, and downstream usage, followed by the endpoint. Every clause carries information and 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 read-only list call with one optional parameter and no output schema, the description supplies the returned field set and the identifier-chaining convention, which is what an agent needs. Account selection is deferred to the schema, leaving only minor gaps like ordering or pagination.

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% and the single optional 'email' parameter is fully documented there, so the baseline is 3. The description implies the tool operates against one Flow account but adds no fallback or multi-account syntax detail beyond the schema.

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 characters saved on a Google Flow account') and goes further by enumerating what each entry contains (reference id, name, images, voice). The resource noun 'characters' cleanly separates it from sibling list tools such as flow_list_voices and flow_list_assets.

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 how to consume the result: pass the id as character_N to flow_agent_chat and reference it as @character_N, which routes the agent to the correct sibling. It stops short of stating when not to use this tool or the prerequisite that identifiers come from this call, so it is strong 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.