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

Goes well beyond the readOnlyHint annotation by disclosing conditional return behavior: free illustrations yield a shadcn React command, SVG address, and licence terms; Pro illustrations yield a page and Pro command and never return SVG even with include_svg. It also discloses licensing (free for commercial use, no credit), which is behavioral context no annotation provides.

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 with the action and sequencing front-loaded, then the free/Pro return contract. No redundant restatement of the title or 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?

There is no output schema, and the description carries that burden fully by enumerating what is returned for both illustration tiers, including the negative case for SVG. An agent has everything needed to call it and interpret the result.

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 coverage is 100%, so baseline is 3, but the description adds a consequence the schema only hints at — that include_svg is not merely ignored but that Pro never returns SVG at all. The id sourcing from find_illustrations reinforces rather than adds to the schema text.

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 ("Get the install details for one Illos illustration by its id") and explicitly names the sibling find_illustrations as the search alternative, so the agent can route without opening either 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?

Gives an explicit sequencing rule ("Use it after find_illustrations, once you have picked an id and need to add it") plus a when-not rule ("to search, use find_illustrations instead"). Both the trigger and the exclusion are stated.

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