Marseille: Three-Card

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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so safety is covered. The description adds genuinely useful non-schema context: the POST endpoint and a cost of 10 credits (Tier 1), which matters for tool selection. It does not disclose randomness behaviour or how the result is produced, so it adds some but not rich context.

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?

One-line spread statement is front-loaded and waste-free, followed by a compact metadata block. The endpoint line is arguably boilerplate for an MCP caller, but overall it is well under any verbosity threshold.

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?

An output schema exists, so return values needn't be described. However, for a 4-parameter, zero-required generative draw tool, the description leaves the agent without guidance on parameter behaviour (seed, question, allowReversed) or on spread selection, which is a real gap given the very dense tarot sibling cluster.

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 only 25% — just 'art' is documented in-schema. The description says nothing about seed (deterministic replay?), question (what it is used for, length limits), or allowReversed (whether reversed cards are drawn, default true), so it fails to compensate for the coverage gap on three of four parameters.

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?

Names the specific resource — a Past/Present/Future three-card Marseille spread — which cleanly distinguishes it from siblings like draw_single, draw_seven_card, draw_celtic_cross or the Rider-Waite three-card variant. It is a noun phrase with no explicit verb ('draw'), but the tool name and group tag supply that, so an agent can tell what it produces.

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?

No statement of when to use this spread versus draw_single, draw_love, draw_decision or draw_seven_card. The 'Past / Present / Future' labels weakly imply a timeline/process question, but the agent must infer that entirely; there are no exclusions, prerequisites, or sibling routing.

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