Appen records 665,840 monthly visits with +0.2% month-over-month growth and Contact for Pricing pricing. mcp.so records 286,704 monthly visits with -3% growth and Free pricing.
Human-validated training data and evaluation services for frontier AI models
Discover and share Model Context Protocol servers for AI agents and coding tools
| Dimension / Metric | | |
|---|---|---|
| Official Domain | appen.com | mcp.so |
| Pricing Model | Contact for Pricing | Free |
| Monthly Visits | 665.84K (665,840) | 286.7K (286,704) |
| MoM Traffic Delta | +1.1K (+0.2%) | -8.96K (-3%) |
| Primary Market & Share | 🇺🇸 United States (22%) | 🇺🇸 United States (11.5%) |
| Direct Visits / mo | 238.31K | 107.65K |
| User Rating | 4.4 | 4.2 |
| Supported Platforms | Website | Website |
Human-validated training data and evaluation services for frontier AI models
Chain-of-thought reasoning traces, SME-level RLHF, supervised fine-tuning demonstrations and adversarial red teaming for the most capable models.
Golden trajectories, RL environment design, failure-mode taxonomies and software-engineering-driven deep evaluation for autonomous agents.
Multilingual ASR and conversational speech data, expressive TTS annotation, vision-language model training data, video action labelling and voice-agent evaluation.
LiDAR point-cloud labeling, multi-camera sensor fusion, robot demonstration trajectories, world-model rollouts and embodied interaction logs.
Discover and share Model Context Protocol servers for AI agents and coding tools
Find servers by name, category, tag, runtime or integration, with featured, trending and newest sections that track community activity.
Review hosted MCP endpoints, authentication requirements and per-client setup instructions before you connect anything.
Discover MCP-compatible clients, official command-line tools, agent loops and reusable Claude/Codex skills in dedicated sections.
Maintainers can publish new servers and claim existing listings so entries stay accurate and attributable.
SpecialistConnects teams directly with verified human participants for preference tuning and studies, but lacks managed end-to-end labeling pipelines.
SpecialistConnects teams directly with verified human participants for preference tuning and studies, but lacks managed end-to-end labeling pipelines.
Blends custom software with dedicated human expert teams to handle complex operations, but operates as a bespoke service.
Blends custom software with dedicated human expert teams to handle complex operations, but operates as a bespoke service.
Combines robust data labeling tools with automated workflows, but focuses more on software tooling than managed human workforces.
Combines robust data labeling tools with automated workflows, but focuses more on software tooling than managed human workforces.
Provides enterprise-grade AI training data and model evaluation at massive scale, but often with higher enterprise pricing.
Provides enterprise-grade AI training data and model evaluation at massive scale, but often with higher enterprise pricing.
SpecialistCurated directory and search engine cataloging thousands of general AI products rather than MCP developer integrations.
SpecialistCurated directory and search engine cataloging thousands of general AI products rather than MCP developer integrations.
SpecialistMassive general AI tools directory, offering broader software discovery but less focus on specific MCP servers.
SpecialistMassive general AI tools directory, offering broader software discovery but less focus on specific MCP servers.
Free / Open-sourceIndependent public directory indexing open-source agent skill files and MCP integrations for AI developers.
Free / Open-sourceIndependent public directory indexing open-source agent skill files and MCP integrations for AI developers.
Delivers advanced multimodal data curation and annotation infrastructure, but requires your own annotation workforce for labeling tasks.
Delivers advanced multimodal data curation and annotation infrastructure, but requires your own annotation workforce for labeling tasks.
SpecialistAgent observability, evaluation, and continuous improvement for production AI
SpecialistAgent observability, evaluation, and continuous improvement for production AI
SpecialistThe multimodal data layer for computer vision and physical AI teams
SpecialistThe multimodal data layer for computer vision and physical AI teams
SpecialistDeveloper-focused AI tools directory and pricing tracker, though less dedicated to community-contributed MCP server lists.
SpecialistDeveloper-focused AI tools directory and pricing tracker, though less dedicated to community-contributed MCP server lists.
SpecialistMarketplace connecting users with ready-made AI agents and starter kits, but with fewer raw developer MCP tools.
SpecialistMarketplace connecting users with ready-made AI agents and starter kits, but with fewer raw developer MCP tools.
