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

With annotations only declaring the readOnly/destructive/openWorld flags, the description adds substantial non-obvious behavior: it consumes the app scan quota (20/month Free), specifies accepted encodings and a 2 MB cap, and pins down the response content (matched print version, FIRST_EDITION when the stamp is read, PokéItem NM-raw fair value only, never marketplace listings). It also explicitly denies a side effect an agent might assume ('Does not add the card'), which resolves the ambiguity created by readOnlyHint=false.

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 sentences, all front-loaded with the identification purpose and constraints first, then cost, then output, then the follow-up handoff. No filler or restatement of the title.

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 fills that gap by describing what is returned (print version plus NM-raw fair value, no listings). Combined with quota cost, input constraints, and the add_card handoff, an agent has everything needed to call this correctly.

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 50%; the schema only says 'base64 or data URL' for image, and the description compensates by adding accepted formats (jpeg/png/webp) and a max 2 MB size limit, which an agent needs before calling. The second parameter, language, is undocumented in both schema and description, leaving one gap.

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?

The description opens with a specific verb+resource ('Identify a card from a photo') and immediately bounds the input domain (base64/data URL, jpeg/png/webp, max 2 MB). It also distinguishes itself from the nearest sibling by stating 'Does not add the card; call add_card with cardId + version after,' so an agent can separate this from add_card and lookup_card without opening schemas.

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?

Usage context is clear — this is the photo-based identification path, and the description explicitly routes the follow-up step to add_card with the returned cardId + version. It does not explicitly contrast with lookup_card for text-based lookups, so the alternative-selection guidance is implied rather than stated.

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