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

Goes beyond the annotations by disclosing image constraints (landscape, >=1200 px wide) and the one-time upload-link fallback, neither of which is expressed in the schema or annotations. It is silent on whether an existing cover image is replaced and on any permission requirements for a draft, which slightly limits the behavioral picture.

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?

Four sentences, each carrying distinct information (action, input modes, validation constraints, optionality/fallback), with the core action front-loaded and no repetition of schema content.

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?

There is no output schema, and the description covers the non-obvious return path (one-time upload link) plus the constraints and fallback behavior, which is enough to call the tool correctly. It remains silent on lifecycle details such as whether re-adding replaces an existing image or whether this only works while the release is in draft.

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 real meaning: it frames image_url and image_file as alternative modes and explains the behavior when both are omitted (upload link), which the schema alone does not convey.

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 ('Adds a cover image') and scopes it to 'a draft press release', which cleanly separates it from siblings like create_release, publish_release, and update_release. An agent can identify the operation without opening the schema.

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?

Explains the three input modes (URL, attached file, or neither to get a one-time upload link) and explicitly notes the step is optional because a default logo/headline cover is used otherwise. It does not reference sibling tools or the surrounding publish workflow, so it stops short of full alternatives guidance.

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