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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds substantive context beyond them: inputs are processed server-side but not stored or logged, no account access, no message sending, unsupported blocks remain literal, URLs and code are preserved. It also states the exact transformation semantics with a concrete input/output example, which is the kind of behavior an agent cannot get from 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?

Front-loaded with the purpose, then pre-call rules, example, post-call rule, capabilities, then limits — a sensible order. It is somewhat verbose and the **Meeting tomorrow** example duplicates the schema description almost verbatim, costing a little density.

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?

Even though an output schema exists, the description goes further and tells the agent how to present the result (verbatim in a plain-text fence), plus input invariants and explicit non-capabilities. For a two-parameter transform tool, an agent has everything needed to call it 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% — `text` is documented in the schema, `locale` is not. The description compensates heavily for `text` by restating the unchanged-copy rule and repeating the escaped-punctuation example, but it never mentions `locale` or what language selection affects, leaving that half of the gap unaddressed.

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 first sentence gives a specific verb and resource: convert the user's Markdown source into WhatsApp-ready text. It further delimits scope by stating it does not render HTML, summarize, translate, or send messages. It never names the closest sibling (style_whatsapp_text) as an alternative, so the differentiation is inferred rather than stated.

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?

It gives explicit pre-call guidance ('copy the supplied source unchanged… do not Markdown-escape or pre-convert') and post-call guidance ('display structuredContent.formattedText verbatim in a plain-text fenced code block'). What is missing is a when-to-use-this-vs-sibling statement, e.g. versus style_whatsapp_text or generate_whatsapp_link.

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