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

With no annotations, the description carries the full burden, and it does add real value: it discloses that results come from a local database and flags returned content as untrusted user-generated input, which is a meaningful safety cue. It omits ordering, pagination, empty-result behavior, and any auth/rate-limit 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?

Two short sentences, no filler, with the core purpose front-loaded and the safety caveat placed after it. Every clause earns its place.

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 simple two-parameter search with no output schema and no annotations, the description covers purpose, scope, and trust handling adequately. It still leaves an agent unsure about result ordering, match behavior, and whether results are paginated, which matters given the 100-row cap.

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 both parameters (query, limit) are already documented with types and the 1-100 bound. The description's 'by username or full name' mildly clarifies what the query matches, but adds no matching semantics (partial vs exact, case sensitivity) beyond the schema baseline.

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 ('Search Instagram users by username or full name') and adds scope ('local database'), which distinguishes it from live-lookup siblings like get_user_by_username. It does not explicitly name sibling alternatives such as search_users_by_demographics or search_tt_users, so an agent must infer the boundary itself.

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?

Usage is only implied: the phrase 'by username or full name' hints at fuzzy/partial lookup versus the exact-match get_user_by_username sibling, but no when-to-use or when-not-to-use guidance is given. No prerequisites, no exclusion of the demographic or TikTok search variants.

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