Generate alt text from an image URL

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

Annotations already cover readOnly=false, openWorld=true and idempotent=false, so the bar is lower. The description still adds real value by disclosing the cost model ('Uses 1 credit from the AltTextGeneratorAI account'), which an agent needs before spending credits. It stops short of explaining failure behavior for unreachable URLs.

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?

Two sentences, no filler, with the input constraint stated first and the credit cost second. Every clause earns its place.

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 two-parameter tool with no output schema, the description covers the input constraint and the credit cost, and annotations supply the safety/open-world profile. It is nearly complete, though it never indicates what is returned (alt text string) or what happens when the URL is unreachable.

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%, including the language default and the 130+ language note, so the schema carries the parameter semantics. The description adds only the 'one image' scope and no extra syntax or format detail, making the baseline 3 appropriate.

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 (writes) and resource (SEO-friendly, accessible alt text) and narrows the input to one image at a public http(s) URL. The URL constraint implicitly separates it from generate_alt_text_from_file, though the sibling is never named outright.

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?

The public-URL constraint implies the right context (use when the image is remotely hosted), but there is no explicit when-to-use/when-not statement and no mention of the file-based alternative or of check_credits for balance checks. Usage is inferred rather than stated.

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