discord_set_guild_banner

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

Goes well beyond the annotations: discloses that Discord rejects the call outright rather than silently ignoring it when the BANNER feature is absent, and states the required permission. It also reports the return value, which is extra context on top of the already-declared idempotent and non-destructive hints.

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 tight sentences, front-loaded with the action, then the critical limitation, then the prerequisite and return value. No filler and each sentence carries distinct information.

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-field mutation with full schema coverage and an output schema, this covers everything an agent needs: what it does, the gating feature requirement, permission scope, failure mode, and result. Nothing material is missing.

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 image format/size, guild_id snowflake pattern, and the audit-log reason are already fully documented in the schema. The description adds no parameter-level detail beyond mentioning the return URL, so 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 ('Set or replace the server's banner') and immediately clarifies what a banner is (the wide image on the landing page). This cleanly distinguishes it from siblings like discord_set_guild_icon and discord_remove_guild_banner.

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 concrete preconditions for use: Manage Server permission and the BANNER feature (boost level 2+). It clearly implies when not to bother (servers without the feature will error), but never explicitly names the sibling alternative such as discord_remove_guild_banner or discord_set_guild_splash.

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