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 structurally. The description still adds real behavioral context: no arguments required, no key or credit needed, and a hard limitation on processing custom data. It stops short of describing the demo's fixed dataset or output shape, but the added constraints are genuinely useful.

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, both front-loaded with the most decision-relevant facts (what it does, then the alternative routing). No padding or repetition 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?

For a zero-argument, read-only demo whose annotations already carry the safety profile, nothing needed for correct invocation is missing. The routing to reconcile_tables covers the one decision an agent has to make.

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?

Zero parameters, so the baseline is 4. The description reinforces this with 'No arguments, key or credit,' removing any ambiguity about whether credentials or inputs are expected.

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?

Specific verb and resource: 'Join the bundled fixed tables and show changed and unmatched records' tells the agent exactly what happens. It explicitly distinguishes itself from reconcile_tables by naming that sibling and the condition (custom data) that selects it.

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?

States when to use it (free, no key, bundled data) and when not to ('This cannot process custom data; use reconcile_tables with a paid key for your files'). The alternative and the switch condition are both explicit.

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