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

Beyond the readOnly/destructive annotations it discloses auth/plan requirements, case- and punctuation-insensitive matching, the payload contents (short def, Markdown long def, related terms, guides, public url), and precise error semantics for TERM_NOT_FOUND. That is meaningful added context, though it could say more about response size or whether related-term links are slugs.

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 dense paragraph with zero filler and a useful failure-mode sentence at the end. The "Free: works without an API key or Pro plan" preamble is front-loaded ahead of the actual purpose, which slightly delays the agent's core identification of what the tool does.

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 single-parameter, read-only lookup with an output schema and full annotation coverage, the description supplies everything an agent needs: input forms, matching rules, return fields, and how to interpret a not-found result. Nothing material is left to inference.

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 already 100%, so baseline is 3; the description earns an extra point by explaining that the single argument accepts any of three forms — glossary slug, literal term, or common alias — and that matching normalizes case and punctuation, which the schema does not state.

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?

States a specific verb and resource ("Looks up a term in the Signal8 Academy glossary") and enumerates the domain covered with concrete examples ("ATM offering", "baby shelf", "full ratchet"). This clearly separates it from data-bearing siblings like get_dilution_coverage or get_learn_guide, which return company/guide content rather than term definitions.

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?

Gives explicit entry conditions ("Free: works without an API key or Pro plan") and tells the agent what inputs are acceptable (slug, term, alias). It also routes on failure — a TERM_NOT_FOUND means the wording is missing, and "the Academy guide search may still cover it" — though it does not name search_learn_guides or get_learn_guide explicitly as the alternative tool.

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