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

Annotations already provide readOnlyHint=true and destructiveHint=false, so the bar is lower. The description adds genuinely useful behavioral context beyond that: 'The API draws the exact number of cards you specify and maps them to your custom positions' and 'No pre-generated summary provided - you interpret the reading based on your interpretation.' This warns the caller about an important respects of the response shape. No contradiction with the annotations.

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?

The definition opens efficiently with the core purpose, but then loads a large paragraph of overlapping use-case lists (chakra readings, lunar, phases, elements, goals, shadow work, inner child, decision matrices...). Several sentences say essentially the same thing: 'this is flexible for custom needs.' It would earn a higher score with trimmed examples and a more tightly structured layout.

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?

Given six parameters, no output schema, and the read-only annotations, the description covers the essential behavioral contract: custom positions, card count matching, no auto-summary, and the maximum position limit. It gives a good enough picture for an agent to select and invoke this tool. The lack of detail about the exact response card structure is minor, since behavioral expectations are already disclosed.

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 the baseline is 3. The description adds a little param-relevant context ('Each position requires a name and interpretation... no more than 10 positions') but largely re-states what the schema already documents. It adds nothing about lang, seed, compact, question, or spreadName beyond their existing schema descriptions.

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 opening sentence, "Build and perform your own custom tarot spread with personalized positions and interpretations (1-10 cards)," states a specific verb, resource, and scope. The 'custom' framing clearly differentiates it from siblings like post_tarot_spreads_celtic_cross or post_tarot_daily, which presumably serve fixed layouts. The use-case list (therapists, coaches, app developers) further disambiguates its niche.

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 description gives clear context for when to use: 'anyone wanting to design specialized layouts beyond traditional spreads' and repeatedly contrasts with standard configurations. However, it never names a sibling alternative explicitly (e.g., 'for standard spreads use post_tarot_spreads_love'), and there is no explicit about 'when not to use this'. It provides solid implied usage but lacks explicit exclusions/names.

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